WO2020256395A2 - Carbon-silicon composite oxide composite for lithium secondary battery anode material, and preparation method therefor - Google Patents

Carbon-silicon composite oxide composite for lithium secondary battery anode material, and preparation method therefor Download PDF

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WO2020256395A2
WO2020256395A2 PCT/KR2020/007824 KR2020007824W WO2020256395A2 WO 2020256395 A2 WO2020256395 A2 WO 2020256395A2 KR 2020007824 W KR2020007824 W KR 2020007824W WO 2020256395 A2 WO2020256395 A2 WO 2020256395A2
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silicon
carbon
composite oxide
negative electrode
secondary battery
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WO2020256395A3 (en
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오성민
임종찬
박정규
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대주전자재료 주식회사
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/364—Composites as mixtures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/483—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides for non-aqueous cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to a carbon-silicon composite oxide composite for a lithium secondary battery negative electrode material and a method for manufacturing the same, and more particularly, by reacting a mixture of Si/SiO 2 silicon raw material powder and metal magnesium in a gaseous state, silicon oxide (SiO X , 0 ⁇ x ⁇ 2) containing silicon particles, MgSiO 3 (enstatite) and/or Mg 2 SiO 4 (forsterite) crystals, and the surface of which is coated with carbon for a secondary battery negative electrode material carbon silicon composite oxide and its manufacturing method will be.
  • Carbon-based, silicon-based, tin-based, transition metal oxides, etc. are mainly researched and developed as negative electrode active materials of the lithium secondary battery.
  • the negative electrode active material developed so far has a lot of room for improvement as the capacity, initial charge/discharge efficiency, expansion rate, and life characteristics do not reach satisfactory levels.
  • materials such as Si, Ge, and Sn, which are Group 4 semiconductor materials, are attracting attention as new anode materials because they have high theoretical capacity.
  • silicon shows high capacity performance of 4,200 mAh/g, and carbon-based It is drawing attention as a next-generation material to replace the anode material of
  • Patent Document 1 a technique of compounding silicon with carbon by a mechanical milling process and coating the surface of silicon particles with a carbon layer using a chemical vapor deposition method (CVD) is also proposed (Patent Document 1), but charging/discharging There is a limit to suppressing volume expansion and contraction accompanying poetry.
  • CVD chemical vapor deposition method
  • silicon oxide has a smaller capacity than silicon, but has a capacity (about 1500 mAh/g) several times higher than that of a carbon-based cathode capacity (about 350 mAh/g), and silicon nanocrystals in a silicon dioxide matrix With this uniformly dispersed structure, it has been in the spotlight as a material with significantly improved volume expansion and life (capacity retention) characteristics compared to other silicon-based materials.
  • lithium and silicon oxide react during initial charging to generate lithium oxide (including lithium oxide and lithium silicate), and the generated lithium oxide is reversibly It will not return to the positive pole. Therefore, lithium is lost due to this irreversible reaction, so that the initial charge/discharge efficiency (ICE) falls below 75%, so that the capacity of the positive electrode is excessively required in designing a secondary battery. There was a problem of offsetting the high capacity per mass.
  • Patent Document 2 As a method for improving the initial charging/discharging efficiency of silicon oxide (SiO x ), there is a method of preparing a Si-SiO x -Li-based composite by reacting SiO x with metal lithium powder (Patent Document 2). By this, the initial efficiency is improved, but there is a problem that the battery capacity is reduced, the stability of the paste at the time of electrode manufacturing is poor, and industrial production is difficult due to difficulty in handling.
  • the SiO x powder is reacted with magnesium hydride (MgH 2 ) or calcium hydride (CaH 2 ) to prepare a silicon-silicon oxide composite containing magnesium or calcium (Patent Document 4) Is being reported.
  • MgH 2 magnesium hydride
  • CaH 2 calcium hydride
  • Patent Document 4 the incorporation of oxygen is reduced during the reaction of SiO x powder and MgH 2 or CaH 2 , but the silicon crystal size rapidly grows due to the local exothermic reaction and Mg or Ca is distributed unevenly, so the capacity retention rate compared to SiO x is reduced. Appeared to fall.
  • carbon-based materials including artificial graphite, natural graphite, and hard carbon, through which lithium can be inserted and released as a negative electrode active material, have been applied.
  • graphite such as artificial graphite or natural graphite has a discharge voltage of -0.2 V compared to lithium, and a battery using graphite as a negative electrode active material exhibits a high discharge voltage of 3.6 V, which is preferable in terms of energy density of a lithium secondary battery. Also, it is most widely used to guarantee the life of a lithium secondary battery due to its excellent reversibility.
  • oxide anode active materials have been recently developed.
  • the amorphous tin oxide negative electrode active material has a high capacity of 800 mAh/g in mass.
  • this tin oxide has a fatal problem with an initial irreversible capacity of about 50%, and also has ancillary problems such as reduction of some of the tin oxide from oxide to tin metal by charging/discharging, making it more difficult to use a secondary battery. Is losing.
  • Patent Document 5 describes a negative electrode active material of Li a Mg b VO c (0.5 ⁇ a ⁇ 3, 0.12 ⁇ b ⁇ 2, 2 ⁇ 2c-a-2b ⁇ 5).
  • Patent Document 6 discloses a negative electrode active material for a lithium secondary battery comprising a carbon material and a composite composed of ultrafine silicon-like particles and oxides containing the silicon-like particles.
  • silicon oxide is reduced through mixing or thermodynamic reaction through a mechano chemical process to prepare a composite composed of ultrafine silicon particles and oxides surrounding the silicon oxide.
  • the silicon oxide (SiO x ) of the starting material is completely reduced to the silicon phase through a reaction, and in this case, it may have a favorable effect on the initial efficiency, but the expansion of the active material and the resulting mechanical deterioration are relatively large. Because of this, it causes a problem that adversely affects the lifespan.
  • M is Mg, Ca
  • Patent Document 8 describes a manufacturing process of a silicon-based compound constituting the negative electrode active material. First, an M-containing compound (M is Mg, Ca, or a mixture thereof) is added to the mixture of SiO 2 and Si, and then heat - treated together to obtain Si (1-y) M y O 1+x .
  • M Mg, Ca, or a mixture thereof
  • the generation of silicon composite oxide is through a gas phase reaction of a silicon/silicon dioxide raw material powder mixture and metallic magnesium, that is, through a reaction of magnesium vapor and silicon oxide vapor, which is formed by mixing silicon powder and silicon dioxide powder. It is made and produces a silicon composite oxide of a uniform composition.
  • the present invention uses silicon oxide as a raw material and includes silicon particles, MgSiO 3 (enstatite) and Mg 2 SiO 4 (forsterite) crystals.
  • the present invention is a silicon composite oxide comprising a silicon-based active material, a silicon oxide-based active material (SiO X , 0 ⁇ x ⁇ 2) and a magnesium silicate crystal in order to solve the above problems, the surface is coated with carbon, and the A carbon-silicon composite oxide composite for a secondary battery negative electrode material is provided in which the atomic ratio of each element constituting the silicon composite oxide satisfies the following relationship.
  • the present invention is a silicon composite oxide including a silicon-based active material, a silicon oxide-based active material (SiO X, 0 ⁇ x ⁇ 2), and a magnesium silicate crystal in order to solve the problems of the silicon composite oxide for negative electrode material of the conventional secondary battery as described above.
  • the surface of the silicon composite oxide is uniformly coated with carbon, and the atomic ratio of each constituent element of the carbon-silicon composite oxide is 0.5 ⁇ (oxygen atomic ratio) / (silicon atomic ratio) + (magnesium atomic ratio) It is characterized by satisfying the range of ⁇ 1.50.
  • the range of (oxygen atomic ratio) / ⁇ (silicon atomic ratio) + (magnesium atomic ratio) ⁇ is preferably 0.5 to 1.05, and 0.7 to 1.00. It is more preferable.
  • the range of (oxygen atomic ratio) / ⁇ (silicon atomic ratio) + (magnesium atomic ratio) ⁇ exceeds 1.50, the portion occupied by the loss capacity during the reaction with lithium increases and the initial efficiency may be deteriorated. Not. If the range of (oxygen atomic ratio) / ⁇ (silicon atomic ratio) + (magnesium atomic ratio) ⁇ is less than 0.5, initial efficiency is lowered, which is not preferable.
  • a silicon composite oxide is synthesized by a uniform gas phase reaction of the evaporated particles by heating the Si/SiO 2 raw material powder mixture and magnesium together, and while the magnesium is locally excessively mixed in the solid phase reaction (oxygen atomic ratio) / ⁇ It is possible to improve the capacity retention rate by preventing rapid growth of silicon due to an exothermic reaction that occurs while (silicon atomic ratio) + (magnesium atomic ratio) ⁇ is maintained within a certain range.
  • the range of (silicon atomic ratio) /(magnesium atomic ratio) ⁇ is preferably in the range of 2.0 to 25.0.
  • the present invention forms a carbon film on the surface of the silicon composite oxide obtained after reacting a raw material powder mixture obtained by mixing silicon powder and silicon dioxide powder with metal magnesium to obtain a silicon composite oxide. Therefore, it is characterized in that the carbon film does not contain magnesium or an oxide component thereof.
  • the present invention synthesizes silicon composite oxide in a uniform gas phase reaction of particles by heating a raw material powder mixture and metal magnesium to deposit on a substrate inside the reactor, thereby causing an exothermic reaction that occurs when magnesium is excessively mixed like a solid-phase reaction. It is characterized by preventing growth.
  • silicon is included as a silicon-based active material. This is because since the silicon phase charges/discharges lithium, it is difficult to express the battery capacity if the silicon phase does not exist.
  • the silicon phase may be from crystalline to amorphous, but since the expansion and contraction during charging/discharging is small and battery performance is high, an amorphous or close phase is preferable.
  • the conventional silicon oxide-based active material is expressed as (SiO X, 0 ⁇ x ⁇ 2), and is prepared in a structure in which amorphous silicon of several nm to tens of nm is finely dispersed in silicon oxide when analyzed by X-ray diffraction. Therefore, the battery capacity is smaller than that of silicon, but is 5 to 6 times higher on a mass basis compared to carbon, and further, the volume expansion is small, and it is easy to use as a negative electrode material.
  • silicon oxide has a large reversible capacity and a very low initial efficiency of about 70%, when a battery is actually manufactured, the battery capacity of the positive electrode is excessively demanded, and the battery capacity corresponding to a 5 to 6 times increase in capacity per active material. could not expect an increase.
  • the practical problem of silicon oxide was that the initial efficiency was largely low.
  • a silicon oxide-based active material is not suitable for use as a negative electrode active material for a lithium secondary battery because its irreversible capacity is large and its life is short, and the high rate charging and discharging rate is not good. This is because the diffusion rate of lithium atoms is low because the structural stability during charging/discharging is low.
  • SiOx (0 ⁇ x ⁇ 1) a silicon atom is covalently bonded to an oxygen atom.
  • SiOx (0 ⁇ x ⁇ 1) a silicon atom is covalently bonded to an oxygen atom.
  • the SiOx (0 ⁇ x ⁇ 1) structure is not destroyed even if a lithium atom is inserted. That is, since the reaction with SiOx (0 ⁇ x ⁇ 1) and lithium atoms proceeds while maintaining the SiOx (0 ⁇ x ⁇ 1) structure, the cycle life and capacity can be increased.
  • the silicon oxide-based active material is an insulator, it is necessary to impart conductivity by some means.
  • a chemical vapor deposition (CVD) method of the silicon composite oxide in organic gas and/or vapor is preferable, and the organic gas and/or vapor in the reactor during heat treatment You can do it efficiently by introducing
  • the amount of carbon coating that affects the conductivity but also the uniformity of the film. For example, even if a sufficient amount of carbon can be obtained, if the film is uneven and the surface of the silicon oxide-based active material is partially exposed, the portion is insulated and adversely affects charge/discharge capacity and cycle characteristics.
  • the silicon-based active material that is, the silicon oxide-based active material having a structure in which silicon particles are dispersed in the silicon oxide-based active material
  • the silicon oxide-based active material is silicon oxide.
  • the silicon oxide-based active material may include silicon oxide and silicon oxide represented by the formula SiOx (0 ⁇ x ⁇ 2).
  • the silicon oxide can be obtained by heating a mixture of silicon dioxide and silicon metal to cool and precipitate a silicon oxide gas generated.
  • Silicon oxide is preferably amorphous.
  • the pulverization of the silicon oxide can be prevented or alleviated, even when the volume of the silicon oxide including the silicon is changed due to the insertion and removal of lithium, and the silicon It is possible to prevent or reduce side reactions between the and electrolyte.
  • the silicon oxide-based active material causes an irreversible reaction with lithium ions when discharged in amorphous to form Li-Si-O or Si + Li 2 O. Therefore, as the content of the silicon oxide-based active material increases, there is a problem that the initial irreversible reaction increases and the initial efficiency decreases.
  • the silicon oxide-based active material is preferably contained in an amount of 5 to 45 mol% in the silicon composite oxide.
  • the content of the silicon oxide-based active material is less than 5 mol%, volume expansion and lifespan characteristics are deteriorated, which is not preferable, and when it exceeds 45 mol%, the initial irreversible reaction increases, which is not preferable.
  • silicon dioxide SiO 2
  • metal magnesium and MgSi alloys are highly reactive due to activity, and they react with members during battery fabrication, making handling difficult. Therefore, the composition of magnesium-doped silicon oxide-based negative electrode materials is strictly controlled so that silicon dioxide, metallic magnesium, and MgSi alloys do not occur, but in reality there is a risk of occurrence of silicon dioxide, metallic magnesium, and MgSi alloys due to uneven element concentration distribution. have.
  • silicon dioxide it is preferable not to include silicon dioxide, because the formation of lithium silicate is suppressed when silicon is inserted, thereby improving initial efficiency.
  • silicon dioxide When silicon dioxide is included, lithium silicate is produced by reacting with lithium, resulting in an irreversible reaction, resulting in lower initial efficiency.
  • one selected from methane, ethane, propane, butane, ethylene, propylene, butadiene, methanol, ethanol, propanol acetylene, benzene and toluene, or a combination thereof is used to form the silicon composite oxide. It is characterized by reacting in a gaseous state at 600 to 1200° C., which will be described in detail below.
  • the carbon layer is preferably formed of graphene, reduced graphene oxide or/and carbon nanofibers as a main component, and the following Chemical Formulas 1, 2 and It changes depending on the carbon source reaction gas represented by Chemical Formula 3, the reaction time, and the reaction temperature.
  • n is an integer of 1 to 20, A is 0 or 1,
  • n is an integer of 2 to 6
  • A is 0 or 1
  • x is 0 or an integer of 1 to 20
  • y is 0 or an integer of 1 to 20
  • z is 0, 1 or 2.
  • the compound represented by Formula 1 and the compound represented by Formula 2 are, for example, at least one selected from the group consisting of methane, ethane, propane, butane, ethylene, propylene, butadiene, methanol, ethanol, and propanol.
  • the oxygen-containing gas represented by Formula 3 is, for example, carbon dioxide (CO 2 ), carbon monoxide (CO), water vapor (H 2 O), and benzyl alcohol, and the gas not containing oxygen represented by Formula 3 is, for example, Acetylene, benzene, toluene, xylene or mixtures thereof.
  • a plurality of inert gases selected from the group consisting of nitrogen, helium, and argon may be further included.
  • the oxygen-containing gas may be at least one selected from the group consisting of carbon monoxide, carbon dioxide, and water vapor.
  • the obtained silicon composite oxide for a negative electrode material of a secondary battery according to the present invention may exhibit high conductivity.
  • water vapor content in the gas mixture is not limited, and for example, it is preferable to use 0.01 to 10% by volume based on 100% by volume of the total carbon source gas.
  • the carbon source gas may be, for example, methane; A mixed gas containing methane and an inert gas; Oxygen-containing gas; Alternatively, there may be a mixed gas containing methane and an oxygen-containing gas.
  • the carbon source gas according to an embodiment may be a CH 4 :CO 2 mixed gas or a CH 4 :CO 2 :H 2 O mixed gas.
  • the CH 4 :CO 2 mixed gas may be provided in a molar ratio of about 1: 0.20 to 0.50, and specifically, may be provided in a molar ratio of about 1: 0.25 to 0.45, and more specifically, a molar ratio of about 1: 0.30 to 0.40 Is preferred.
  • the CH 4 :CO 2 :H 2 O mixed gas is provided in a molar ratio of about 1: 0.20 to 0.50: 0.01 to 1.45. Specifically, a molar ratio of about 1: 0.25 to 0.45: 0.10 to 1.35 is preferable. Further, a molar ratio of about 1: 0.30 to 0.40: 0.50 to 1.0 is preferred.
  • the carbon source gas according to another embodiment may be carbon monoxide (C0) or carbon dioxide (CO 2 ).
  • the carbon source gas according to another embodiment is a mixed gas of CH 4 and N 2 .
  • the mixed gas of CH 4 and N 2 is provided in a molar ratio of about 1: 0.20 to 0.50. Specifically, a molar ratio of about 1: 0.25 to 0.45 is preferred. More preferably, it is a molar ratio of about 1:0.30 to 0.40.
  • the carbon source gas according to an embodiment may not contain an inert gas such as nitrogen.
  • the heat treatment is preferably performed at 700 to 1100 °C, for example, 700 to 1000 °C.
  • the pressure in the heat treatment step is also not limited, and it is preferable to select it in consideration of the heat treatment temperature, the composition of the gas mixture, and the desired amount of carbon coating.
  • the pressure during the heat treatment can be controlled by adjusting the amount of the gas mixture flowing out to the amount of the gas mixture flowing in.
  • the pressure during heat treatment may be 1 atm or more, for example, 2 atm or more, 3 atm or more, 4 atm or more, 5 atm or more, but is not limited thereto.
  • the heat treatment time is not particularly limited, and may be appropriately adjusted according to the heat treatment temperature, the pressure during heat treatment, the composition of the gas mixture, and the desired amount of carbon coating.
  • the reaction time may be 10 minutes to 100 hours, specifically 30 minutes to 90 hours, more specifically 50 minutes to 40 hours, but is not limited thereto.
  • the thickness of the formed carbon film increases, thereby improving the electrical properties of the composite.
  • the manufacturing method of the composite includes substantially a large amount of graphene oxide or/and carbon nanofibers reduced by graphene over the entire surface of the silicon-silicon oxide-carbon composite even at a relatively low temperature through the gas phase reaction of the carbon source gas described above. It is preferable because a uniform carbon film is formed. And, the carbon film removal reaction hardly occurs.
  • the carbon film is uniformly formed on the surface of the oxide through the gas phase reaction, a carbon film having high crystallinity can be formed.
  • the structure does not change and the conductivity of the negative electrode active material is reduced. Can be improved.
  • the present invention is characterized in that a carbon film containing substantially a large amount of graphene, reduced graphene oxide, or/and carbon nanofibers (referred to as graphene-containing materials) is formed, but the upper part of the silicon-silicon oxide-carbon composite
  • a reaction gas composed of the carbon source gas is supplied to the graphene-containing material, a graphene-containing material is grown on the surface of a material selected from silicon oxide and its reduction product. As the reaction time elapses, the graphene-containing material is gradually formed to obtain a carbon-silicon composite oxide composite.
  • the structure of the graphene-containing material may be a layer or a nanosheet type, or a structure in which some pieces are mixed.
  • the nanosheet represents a case in which graphene is formed in an irregular state on at least one selected from silicon oxide and its reduction products
  • the film is in the form of a film in which graphene is continuously and uniformly formed on at least one selected from silicon oxide and its reduction products Say.
  • the fragment may refer to a case in which a part of the above-described nanosheet or film is damaged or deformed.
  • the present invention provides a uniform coating of the graphene-containing material on the surface of the present oxide.
  • the carbon-silicon composite oxide composite for a negative electrode material of a secondary battery according to the present invention inhibits volume expansion by directly growing a graphene-containing material having excellent conductivity on the surface of silicon and silicon oxide, which is flexible in volume expansion, and silicon and silicon oxide are pulverized. Can be reduced.
  • SEI solid electrolyte interface
  • the present invention forms a carbon film on the surface of the silicon composite oxide obtained after reacting a raw material powder mixture of silicon powder and silicon dioxide powder with metal magnesium to obtain a silicon composite oxide, so that magnesium or its oxide component is not included in the carbon film. Does not.
  • the raw material powder mixture and the metal magnesium are heated to react in a gaseous state, and deposited on the substrate inside the reactor to synthesize the silicon composite oxide in a uniform gas phase reaction of the particles, the raw material powder and magnesium react evenly, As in the solid-state reaction, magnesium is excessively mixed in the field to prevent rapid growth of silicon due to an exothermic reaction, and microcrystals of silicon are dispersed in magnesium silicate, that is, formed in an enclosed structure, and the expansion of silicon by charging and discharging High battery performance can be obtained by suppressing shrinkage.
  • the anode active material according to the present invention is considered to have a peak due to a silicon crystal in the X-ray diffraction pattern analysis, and the peak appearing in the range of 2 ⁇ > 28° is due to a silicon crystal having a crystal size of 2 to 10 nm.
  • the silicon particles of the silicon-based active material are preferably amorphous and/or 2 to 10 nm particles.
  • it is preferable that fine crystals or particles of silicon are uniformly dispersed.
  • the silicon composite oxide for a negative electrode material of a secondary battery according to the present invention contains silicon particles, it is possible to suppress a large amount of destruction by forming a lithium alloy on a large specific surface area.
  • silicon particles react with lithium to form LiySix (Li 4.2 Si, etc.), and return to the silicon single phase when discharged.
  • silicon fine particles of this size are used as a negative electrode active material for a secondary battery using a non-aqueous electrolyte, the volume change during charging/discharging is suppressed to relieve the stress at the grain boundary, thereby maintaining high initial efficiency and battery capacity.
  • the density of the present composite increases, approaching the theoretical density, and pores are greatly reduced, which is preferable. Through this, the density of the matrix is increased and the strength is strengthened to prevent cracking, thereby improving initial efficiency and cycle life.
  • the silicon composite oxide for a negative electrode material of a secondary battery according to the present invention preferably has a crystallite size of 2 to 10 nm. It is preferable that the fine crystals of silicon are uniformly dispersed. The crystallite size of the silicon particles tends to increase with the addition of magnesium. When the amount of magnesium added exceeds 10% by weight, the crystallite size of silicon increases to 12 to 15 nm.
  • the silicon composite oxide for a negative electrode material of a secondary battery according to the present invention has a structure in which silicon particles are dispersed in a silicon oxide-based active material and magnesium silicate.
  • the silicon content of the carbon-silicon composite oxide composite for a negative electrode material of a secondary battery according to the present invention is preferably 30 to 80% by weight. Further, it is preferably 40 to 70% by weight, particularly 40 to 60% by weight. If it is less than 30% by weight, the charge/discharge capacity of the lithium-ion battery decreases because the amount of the lithium occlusion/release active material is small. In addition, during charging/discharging, the expansion and contraction of the electrode becomes too large, so that the negative electrode active material powder is further finely divided, thereby deteriorating the cycle characteristics.
  • Mg may be included in a ratio of 2 to 20 parts by weight per 100 parts by weight of the total silicon composite oxide according to the present invention.
  • the MgSiO 3 (enstatite) crystal when an X-ray diffraction pattern is analyzed, the MgSiO 3 (enstatite) crystal exhibits a peak attributable to the silicon crystal within a diffraction angle of 28 ° ⁇ 2 ⁇ ⁇ 29 °, and a diffraction angle of 30.5 ° ⁇ 2 ⁇ ⁇ 31.5 ° Within the range, a peak attributed to the MgSiO 3 crystal may appear.
  • the negative electrode active material according to the present invention may further include a Mg 2 SiO 4 (forsterite) crystal.
  • the negative electrode active material according to the present invention contains carbon per 100 parts by weight of the total silicon composite oxide It may be included in 2 to 20 parts by weight.
  • the average thickness of the carbon film may be 5 to 500 nm.
  • a peak due to a silicon crystal appears in an X-ray diffraction pattern analysis, and a peak at a diffraction angle of 2 ⁇ around 28.5 ° is due to a silicon crystal having a crystal size of 1 to 25 nm.
  • the doping amount of magnesium in the carbon-silicon composite oxide composite of the present invention that is, the amount of magnesium contained in the composite, that is, the ratio of magnesium is preferably 1 to 15% by weight. More preferably, it is preferably 4 to 10% by weight.
  • the magnesium content is 1% by weight or more, the initial efficiency can be achieved, and when the content is 15% by weight or less, a decrease in cycle characteristics and a problem in handling safety are not caused, so it is suitable. That is, it is preferable from the viewpoint of stability that the doped magnesium is mainly present as magnesium silicate among the negative electrode materials for nonaqueous electrolyte secondary batteries.
  • the present invention is characterized in that it contains magnesium silicate, magnesium silicate crystals are difficult to react with lithium ions, that is, alloying, so when the negative electrode active material according to the present invention is used as an electrode, the electrode expands when lithium ions rapidly increase. It is preferable because it suppresses and reduces the amount of contraction. This can improve the cycle characteristics.
  • the silicon composite oxide for a negative electrode material of a secondary battery according to the present invention contains magnesium silicate to increase the degree of amorphization of the negative electrode active material, suppress the growth of lithium silicate that may be formed during reduction of the negative electrode active material, and diffusion of lithium atoms. It has the effect of improving the speed. In addition, by suppressing the initial irreversible reaction, the initial capacity, life characteristics, and high rate charging/discharging characteristics of the lithium secondary battery may be improved.
  • the silicon composite oxide for a negative electrode material of a secondary battery according to the present invention contains magnesium silicate and is formed in a continuous phase surrounding the silicon particles
  • the matrix of the silicon composite oxide for the negative electrode material of the secondary battery according to the present invention is strengthened by magnesium silicate. Can be strengthened.
  • the manufacturing method of the composite according to the present invention is characterized in that silicon oxide gas and magnesium gas are simultaneously generated in the same container, and the gas is cooled on the deposition surface and recovered. Silicon oxide and magnesium react uniformly, and as a result, it becomes possible to produce a silicon composite oxide having a uniform element concentration distribution.
  • the silicon composite oxide for a negative electrode material of a secondary battery according to the present invention can suppress a chemical reaction with the negative electrode material and the binder when preparing an electrode paste containing polyimide as a binder including magnesium silicate compared to lithium doping. . Therefore, the stability of the electrode paste manufactured by using such a negative electrode material is increased, and the cycle durability of the negative electrode manufactured accordingly can be improved as compared with the conventional one, which is preferable.
  • the amount of carbon coating (carbon content) for the silicon composite oxide is preferably 2 to 15% by weight.
  • Silicon contained in the carbon-silicon composite oxide composite doped with magnesium and coated with a carbon film in the range of 2 to 15% by weight has a structure in which the crystallites are dispersed in a silicon oxide-based active material in a crystal state of 3 to 20 nm in size. desirable.
  • the average thickness of the carbon coating may be 5 to 500 nm. More preferably, it may be 5 to 200 nm.
  • a carbon film is uniformly formed on the surface of the silicon composite oxide. By forming the carbon film, the initial efficiency and lifespan characteristics of the active material can be improved.
  • carbon is contained in an amount of 2 to 15% by weight per 100 parts by weight of the total silicon oxide complex. It is more preferably 3 to 10% by weight.
  • the carbon content is less than 2% by weight, a sufficient effect of improving conductivity cannot be expected, and there is a concern that the electrode life of the lithium secondary battery may be reduced. If the carbon content exceeds 15% by weight, it is not preferable because the discharge capacity decreases and it is difficult to obtain high energy. Moreover, the bulk density becomes small, and the charge/discharge capacity per unit volume may decrease.
  • the carbon film may include any one or more selected from the group consisting of carbon nanofibers, graphene, graphene oxide, and reduced graphene oxide.
  • the specific gravity of the silicon composite oxide coated with carbon may be 1.8 to 3.2.
  • the specific gravity of the silicon composite oxide coated with carbon that is, the carbon-silicon composite oxide composite is preferably 1.8 to 2.6. More preferably, it is 2.0 to 2.5.
  • the specific gravity is different depending on the amount of carbon coating. When the amount of carbon is fixed, the pores inside the particles decrease when the specific gravity is large, so when used as a negative electrode material, not only the conductivity is improved, but also the strength of the matrix is strengthened, and the initial efficiency or cycle life characteristics can be improved.
  • the specific gravity When the specific gravity is in the range of 1.8 to 2.6, it exhibits a high battery capacity of 900 to 3000 mAh/g and increases the coulomb efficiency. Even when mixed with a graphite-based material having low volume expansion, only the silicon particles are large and do not cause volume expansion, so that the separation of the graphite material and the silicon particles is small, and a nonaqueous electrolyte secondary battery having excellent cycle characteristics can be obtained.
  • the specific gravity is set to 1.8 or more, separation between the negative electrode active material powders due to volume expansion of the negative electrode active material powder during charging is blocked and cycle deterioration is suppressed.
  • the specific gravity is set to 2.6 or less, the impregnation property of the electrolyte solution is improved and the utilization rate of the negative electrode active material is increased, thereby improving the initial charge/discharge capacity.
  • the specific gravity and the true density are expressed in the same meaning.
  • the specific gravity measurement conditions by a dry hydrometer are as follows, for example.
  • Micromatrix Inc.'s Accupit II 1340 can be used as a dry density meter.
  • the gas used is helium, and it is measured in a sample holder set at 23°C.
  • the battery capacity per unit weight of the active material is 1500 to 3000 mAh/g. It is reduced compared to the theoretical battery capacity (4200 mAh/g) per unit weight of the silicon active material, but it can provide a negative electrode of a nonaqueous electrolyte secondary battery with high electronic conductivity and relatively small volume expansion and high cycle characteristics. Even when used in combination with a negative electrode active material, it is preferable because the coulomb efficiency is high and good cycle characteristics can be obtained.
  • the average particle diameter of the silicon composite oxide coated with carbon may be 0.1 to 15 ⁇ m.
  • the carbon-silicon composite oxide composite coated with carbon preferably has an average particle diameter of 2.0 to 10 ⁇ m with a cumulative 50% size D 50 in a volume-based distribution measured by a laser diffraction method. More preferably, it is 2 to 8 ⁇ m.
  • the average particle diameter is a value measured by the cumulative volume average D 50 (that is, the particle diameter or median diameter when the cumulative volume average becomes 50%) in the particle size distribution measurement by laser diffraction method.
  • Dry classification mainly uses airflow, and the processes of dispersion, separation (separation of fine particles and coarse particles), collection (separation of solid and gas), and discharge are performed sequentially or simultaneously, and interference between particles, particle shape, Pre-treatment (adjustment of moisture, dispersibility, humidity, etc.) is carried out before classification so as not to reduce classification efficiency due to confusion of airflow, velocity distribution, and the influence of static electricity. Also, it is used by controlling the moisture or oxygen concentration of the used air stream.
  • a type in which a dry classifier such as a cyclone is integrated can be pulverized and classified at once to obtain a desired particle size distribution. It is effective to remove the coarse and granular side with a classifier or sieve after grinding.
  • initial efficiency and cycle characteristics can be improved by 10 to 20% compared to before classification. It is preferable that the maximum particle diameter (Dmax) of the powder after classification is 20 ⁇ m or less. The specific surface area of this composite powder in this range is reduced. As a result, lithium added to the SEI (Solid Electrolyte Interface) may be reduced.
  • Dmax maximum particle diameter
  • the powder after classification treatment has an amorphous grain boundary and a crystalline grain boundary, and particle collapse in a charge/discharge cycle is suppressed by the stress relaxation effect of the amorphous grain boundary and the crystalline grain boundary. Therefore, by using such powder as a negative electrode material of a nonaqueous electrolyte secondary battery, a nonaqueous electrolyte secondary battery using such powder is preferable because the negative electrode material of the nonaqueous electrolyte secondary battery can withstand the stress of volume expansion change due to charge/discharge.
  • the specific surface area of the silicon composite oxide coated with carbon may be 1 to 40 m 2 /g.
  • the specific surface area of the composite coated with carbon is preferably 3 to 20 m 2 /g.
  • rate characteristics are deteriorated, which is not preferable.
  • the specific surface area of the composite exceeds 20 m 2 /g, the contact area with the electrolyte may increase, thereby accelerating the decomposition reaction of the electrolyte, which is undesirable because a side reaction of the battery may occur. More preferably, it is 4 to 10 m 2 /g.
  • the negative electrode active material according to the present invention contains a carbon-silicon composite oxide composite based on 100 parts by weight of the It may be included in 5 to 70 parts by weight.
  • the negative electrode active material for a lithium secondary battery according to the present invention may reduce the electrical resistance of the negative electrode active material layer and at the same time alleviate the expansion stress caused by charging by mixing the carbon-silicon composite oxide composite and the carbon-based material.
  • the carbon-based material include pyrolytic carbons, coke, carbon fibers, fired organic polymer compounds, and carbon blacks.
  • the content of the carbon-based negative electrode active material in the mixture of the carbon-silicon composite oxide composite and the carbon-based material may be 30 to 95% by weight, preferably 50 to 90% by weight.
  • the lithium secondary battery including the carbon-silicon composite oxide composite of the present invention exhibits high capacity and long life battery characteristics.
  • the present invention also,
  • a fourth step of grinding/classifying the silicon composite oxide prepared in the third step is a fourth step of grinding/classifying the silicon composite oxide prepared in the third step.
  • It provides a method for producing a negative electrode active material for a lithium secondary battery comprising a fifth step of covering the surface of the silicon composite oxide prepared in the fourth step with carbon.
  • the Si / SiO 2 raw material powder mixture in the first step is characterized in that silicon dioxide is mixed in a ratio of 0.2 to 1.5 moles per mole of silicon.
  • the silicon powder and the silicon dioxide powder used in the first step may have an average particle diameter of 10 nm to 0.5 ⁇ m and 10 nm to 100 nm, respectively.
  • Si may contain oxygen, and the Si/SiO 2 raw material powder mixture contains 0.2 to 1.5 moles of silicon dioxide per mole of silicon. Can be mixed with. More preferably, it can be mixed in a ratio of 0.8 to 1.2 mol.
  • the silicon powder and the silicon dioxide powder used in the first step have an average particle size of 50 nm to 50 ⁇ m and 10 to 100 nm, respectively.
  • Si may contain oxygen
  • the Si/SiO 2 raw material powder mixture preferably has an oxygen/silicon atom ratio of 1 to 1.5. , More preferably, the oxygen/silicon atom ratio is 1 to 1.1.
  • SiOx (0.9 ⁇ x ⁇ 1.5) may be used instead of the Si / SiO 2 raw material powder mixture, and SiO may be preferred.
  • the evaporation in the second step may be performed by heating at 600 to 1600° C. under a pressure of 0.00001 to 2 torr.
  • the cooling process in the third step may be cooled to room temperature by any one of cooling by a water-cooled substrate, natural cooling, and other cooling methods.
  • the pulverization process in the fourth step may be pulverized so that the average particle diameter is 2 to 10 ⁇ m.
  • the silicon composite oxide coated with carbon in the 5th step is methane, ethane, propane, butane, ethylene, propylene, butadiene, methanol, ethanol, propanol acetylene, benzene And one selected from toluene or a combination thereof is characterized in that the reaction is performed in a gaseous state at 600 to 1200° C., which will be described in detail below.
  • the carbon layer is preferably formed of graphene, reduced graphene oxide or/and carbon nanofibers as a main component, and the following Chemical Formulas 1, 2 and Chemical Formulas It changes with the carbon source reaction gas represented by 3, reaction time, and reaction temperature.
  • n is an integer of 1 to 20, A is 0 or 1,
  • n is an integer of 2 to 6
  • A is 0 or 1
  • x is 0 or an integer of 1 to 20
  • y is 0 or an integer of 1 to 20
  • z is 0, 1 or 2.
  • the compound represented by Formula 1 and the compound represented by Formula 2 are, for example, at least one selected from the group consisting of methane, ethane, propane, butane, ethylene, propylene, butadiene, methanol, ethanol, and propanol.
  • the oxygen-containing gas represented by Formula 3 is, for example, carbon dioxide (CO 2 ), carbon monoxide (CO), water vapor (H 2 O), and benzyl alcohol, and the gas not containing oxygen represented by Formula 3 is, for example, Acetylene, benzene, toluene, xylene or mixtures thereof.
  • a plurality of inert gases selected from the group consisting of nitrogen, helium, and argon may be further included.
  • the oxygen-containing gas may be at least one selected from the group consisting of carbon monoxide, carbon dioxide, and water vapor.
  • a negative electrode for a lithium secondary battery having a silicon composite oxide for a negative electrode material for a secondary battery according to an embodiment of the present invention is manufactured by the above manufacturing method.
  • a lithium secondary battery according to an embodiment of the present invention includes a negative electrode for a lithium secondary battery.
  • the lithium secondary battery uses a carbon-silicon composite oxide composite for a secondary battery negative electrode material obtained by the above manufacturing method, and may further include graphite as a negative electrode.
  • the carbon-silicon composite oxide composite according to the present invention improves charge/discharge capacity, improves initial charge/discharge efficiency, and improves capacity retention.
  • the silicon composite oxide is synthesized by a uniform gas phase reaction of the evaporated particles by heating the Si/SiO 2 raw material powder mixture and magnesium together, and the exothermic reaction that occurs when Mg is locally excessively mixed as in the solid phase reaction. It is possible to improve the capacity retention rate by preventing the silicon from growing rapidly.
  • the manufacturing method of the silicon composite oxide according to the present invention mainly produces MgSiO 3 (enstatite) rather than the formation of Mg 2 SiO 4 (forsterite), so that Mg 2 SiO 4 is an irreversible material of the silicon composite oxide with a small amount of Mg. It is possible to improve the capacity per unit weight by efficiently controlling (forsterite) and MgSiO 3 (enstatite).
  • Example 1 shows the results of analyzing the surface of the carbon-silicon composite oxide composite prepared in Example 1 of the present invention using a transmission electron microscope (TEM).
  • TEM transmission electron microscope
  • Step 1 Add 8 kg of silicon powder with an average particle size of 20 ⁇ m and 16 kg of silicon dioxide powder with an average particle size of 20 nm in 50 kg of water, stir for 2 hours to uniformly mix, and then at 150°C. Drying for an hour to form a raw material powder mixture.
  • Step 2 Put the raw material powder mixture and 0.6 kg of metal magnesium into crucibles-A and crucible-B of a vacuum reactor, respectively, to reach 0.1 torr by decompressing, and heating to crucible-A to 1500°C The crucible-B was heated to 900° C. and reacted for 5 hours.
  • Step 5 Put 50 g of the pulverized silicon composite oxide powder inside a tube-type electric furnace, and keep argon and methane gas at 900° C. for 1 hour while flowing 1 L/min each, so that the surface is covered with carbon. A carbon-silicon composite oxide composite powder was prepared.
  • the surface of the prepared carbon-silicon composite oxide composite was analyzed using a transmission electron microscope (TEM), and the results are shown in FIG. 1.
  • the content of magnesium (Mg) was analyzed by inductively coupled plasma (ICP) emission spectroscopy, and the content of oxygen (O) and carbon (C) was analyzed by an elemental analyzer, respectively.
  • the magnesium content of the carbon-silicon composite oxide composite prepared in Example 1 was 2.3 wt%, the oxygen content analyzed by the elemental analyzer was 34.1 wt%, and the carbon content was 5 wt%.
  • Example 1 Example 2 Example 3
  • Example 4 Example 5 Comparative Example 1 Comparative Example 2 Comparative Example 3 Mg At% 2.13 5.76 11.12 11.92 5.55 - 1.79 22.63 Si At% 50.49 48.55 44.66 42.13 48.08 50.39 44.91 48.36 O At% 47.38 45.69 44.22 45.95 46.37 49.61 53.30 29 O/(Mg+Si) 0.90 0.84 0.79 0.85 0.86 0.98 1.14 0.41 Si/Mg 23.7 8.43 4.02 3.53 8.67 0 25.09 2.13
  • the average particle diameter (particle diameter) of the prepared powder is measured by the volume average value D 50 (particle diameter or median diameter when the cumulative volume becomes 50% of the total volume) in the particle size distribution measurement by laser light diffraction method. Became.
  • the BET was 6.7 m 2 /g, the specific gravity was 2.3, the D 50 was 6 ⁇ m, and the silicon crystal size by XRD was 9.5 nm.
  • the crystal structure of the carbon-silicon composite oxide composite prepared in Example 1 was analyzed using an X-ray diffraction pattern.
  • the carbon-silicon composite oxide composite prepared in the present invention belongs to the Si crystal at a diffraction angle (2 ⁇ ) of 28.5 ° and a peak attributable to the diffraction angle (2 ⁇ ) 31.0 ° to the MgSiO 3 crystal. It was found that the peak appeared and was composed of crystalline Si and MgSiO 3 .
  • the Si crystal size in the obtained carbon-silicon composite oxide composite is based on the following general formula (1) based on the full width at half maximum (FWHM) of the peak attributable to Si(111) in the X-ray diffraction pattern. It was analyzed by the Sherrer equation expressed as.
  • Example 1 Except for adding 2 kg of metallic magnesium in Example 1, a carbon-silicon composite oxide composite powder was prepared in the same manner as in Example 1.
  • the magnesium content of the prepared carbon-silicon composite oxide composite was 6.2 wt%
  • the oxygen content analyzed by the elemental analyzer was 32.8 wt%
  • the carbon content was 5 wt%.
  • the BET was 5.8 m 2 /g
  • the specific gravity was 2.3
  • the D 50 was 6 ⁇ m
  • the silicon crystal size by XRD was 7.7 nm.
  • Example 1 Except for adding 4 kg of metal magnesium in Example 1, a carbon-silicon composite oxide composite powder was prepared in the same manner as in Example 1.
  • the magnesium content of the prepared carbon-silicon composite oxide composite was 12 wt%
  • the oxygen content analyzed by the elemental analyzer was 31.8 wt%
  • the carbon content was 5 wt%.
  • the BET was 6.3 m 2 /g
  • the specific gravity was 2.4
  • the D 50 was 6 ⁇ m
  • the silicon crystal size by XRD was 8.6 nm.
  • a carbon-silicon composite oxide composite powder was prepared in the same manner as in Example 3, except that the cooling temperature was set to 950°C in Example 3 above.
  • the magnesium content of the prepared carbon-silicon composite oxide composite was 13 wt%
  • the oxygen content analyzed by the elemental analyzer was 33.4 wt%
  • the carbon content was 5 wt%.
  • the BET was 6.3 m 2 /g
  • the specific gravity was 2.4
  • the D 50 was 6 ⁇ m
  • the silicon crystal size by XRD was 10.3 nm.
  • Example 2 a carbon-silicon composite oxide composite powder coated with carbon was prepared in the same manner as in Example 2, except that CVD treatment was performed with natural gas containing methane to coat the surface with carbon.
  • the magnesium content of the prepared carbon-silicon composite oxide composite was 6 wt%
  • the oxygen content analyzed by the elemental analyzer was 20.8 wt%
  • the carbon content was 7 wt%.
  • the BET was 6.2 m 2 /g
  • the specific gravity was 2.3
  • the D 50 was 6 ⁇ m
  • the silicon crystal size was measured to be 8.2 nm by the Sira method of XRD.
  • Example 1 In the second step of Example 1, except that 2 kg of metal magnesium was added to the crucible-B and the crucible-B was heated to 900° C., carbon coated on the surface of the carbon-coated surface in the same manner as in Example 1- A silicon oxide composite was prepared.
  • the oxygen content analyzed by the elemental analyzer of the prepared carbon-silicon oxide composite was 36 wt% and the carbon content 5 wt%.
  • the BET was 6.3 m 2 /g
  • the specific gravity was 2.2
  • the D 50 was 6 ⁇ m
  • the silicon crystal size by XRD was measured to be 4.2 nm.
  • the magnesium content of the prepared carbon-silicon composite oxide composite was 2 wt%
  • the oxygen content analyzed by the elemental analyzer was 39.6 wt%
  • the carbon content was 5 wt%.
  • the BET was 6.7 m 2 /g
  • the specific gravity was 2.3
  • the D 50 was 6 ⁇ m
  • the silicon crystal size by XRD was 9.1 nm.
  • the magnesium content of the carbon-silicon composite oxide composite was 23 wt%
  • the oxygen content analyzed by the elemental analyzer was 19 wt%
  • the carbon content was 4 wt%.
  • the BET was 6.2 m 2 /g
  • the specific gravity was 2.6
  • the D 50 was 7 ⁇ m
  • the silicon crystal size by XRD was measured to be 28 nm.
  • the carbon-silicon composite oxide composite powder prepared according to the above Examples and Comparative Examples and natural graphite were mixed in a weight ratio of 10:90 to prepare a negative electrode for a lithium secondary battery and a battery (coin cell) as an electrode active material.
  • the mixed active material and the binder, carboxyl methyl cellulose (CMC) and styrene butadiene rubber (SBR) were quantified so that the weight ratio was 97:1.5:1.5, and then mixed with water to prepare a negative electrode slurry composition. I did.
  • An electrode having a thickness of 70 ⁇ m was prepared by applying the negative electrode library composition to a copper foil having a thickness of 18 ⁇ m and drying it, and punching the electrode into a circle having a diameter of 14 mm to prepare a negative electrode for a coin cell, Metal lithium foil was used.
  • a porous polyethylene sheet having a thickness of 0.1 mm was used as a separator, and LiPF 6 at a concentration of 1 M was dissolved in a solution in which ethylene carbonate (EC) and diethylene carbonate (DEC) were mixed at a volume ratio of 1:1 as an electrolyte, and used as an electrolyte.
  • EC ethylene carbonate
  • DEC diethylene carbonate
  • a coin cell (battery) having a thickness of 2 mm and a diameter of 32 mm was manufactured by applying the above components.
  • the coin cell prepared for each sample was charged with a constant current of 0.1 C until the voltage became 0.005 V, and discharged with a constant current of 0.1 C until the voltage became 2.0 V, and the charging capacity (mAh/g), Discharge capacity (mAh/g) and initial charge/discharge efficiency (%) were calculated.
  • Silicon oxide (SiOx) prepared without using magnesium in Comparative Example 1 had an initial charge/discharge efficiency of 66%, which was lower than that of the carbon-silicon composite oxide composite of Example containing MgSiO 3 or Mg 2 SiO 4 .

Abstract

The present invention relates to a carbon-silicon composite oxide for a lithium secondary battery anode material, and a preparation method therefor, and, more specifically, to: a carbon-silicon composite oxide for a secondary battery anode material, and a preparation method therefor, the carbon-silicon composite oxide having a surface which comprises silicon particles, MgSiO3 (enstatite) and Mg2SiO4 (forsterite) crystals in silicon oxide (SiOX, 0<x≤2), and which is coated with carbon by causing a gas-phase reaction of a Si/SiO2 material powder mixture and a magnesium metal.

Description

리튬이차전지 음극재용 탄소-규소복합산화물 복합체 및 이의 제조방법Carbon-silicon composite oxide composite for negative electrode material of lithium secondary battery and manufacturing method thereof
본 발명은 리튬이차전지 음극재용 탄소-규소복합산화물 복합체 및 이의 제조방법에 관한 것으로, 보다 상세하게는 Si/SiO 2 규소 원료 분말 혼합체와 금속 마그네슘을 기체상태에서 반응시킴으로써, 규소산화물(SiO X, 0<x≤2) 내에 규소 입자, MgSiO 3(enstatite) 및/또는 Mg 2SiO 4(forsterite) 결정을 포함하고, 표면이 탄소로 피복된 이차전지 음극재용 탄소규소복합산화물 및 이의 제조방법에 관한 것이다.The present invention relates to a carbon-silicon composite oxide composite for a lithium secondary battery negative electrode material and a method for manufacturing the same, and more particularly, by reacting a mixture of Si/SiO 2 silicon raw material powder and metal magnesium in a gaseous state, silicon oxide (SiO X , 0<x≤2) containing silicon particles, MgSiO 3 (enstatite) and/or Mg 2 SiO 4 (forsterite) crystals, and the surface of which is coated with carbon for a secondary battery negative electrode material carbon silicon composite oxide and its manufacturing method will be.
휴대기기의 소형화 및 고성능화, 전기자동차 및 대용량 에너지저장 산업에서도 이차전지의 필요성이 부각되면서 리튬이차전지 성능 향상에 대한 요구가 증대되고 있다. 에너지밀도를 높이기 위하여 양극활물질 및 음극활물질의 고용량화, 극판의 고밀도화, 분리막의 박막화와 충/방전 전압을 높이는 등의 연구개발이 진행되고 있다. 그렇지만, 분리막의 박막화, 극판의 고밀도화와 충/방전 전압을 높이는 것은 이차전지의 안정성에 치명적인 문제를 발생시킬 수 있으므로 현재 기술적인 한계에 도달해 있으며, 양극활물질 및 음극활물질의 용량을 높이는 방향으로 연구개발이 집중되고 있다. 특히 음극활물질은 기존의 흑연계가 갖고 있는 이론용량(372 mAh/g)보다 수배 이상의 용량을 발현할 수 있는 소재들이 보고되고 있다. As the need for secondary batteries has emerged in the miniaturization and high performance of portable devices, electric vehicles and large-capacity energy storage industries, the demand for lithium secondary battery performance improvement is increasing. In order to increase the energy density, research and development such as increasing the capacity of the positive electrode active material and the negative electrode active material, increasing the density of the electrode plate, thinning the separator, and increasing the charge/discharge voltage are being conducted. However, since thinning of the separator, increasing the density of the electrode plate, and increasing the charging/discharging voltage can cause a fatal problem in the stability of the secondary battery, the technical limit is currently reached, and research is directed toward increasing the capacity of the positive electrode active material and the negative electrode active material. Development is focused. In particular, materials capable of expressing a capacity several times more than the theoretical capacity (372 mAh/g) of the existing graphite system have been reported for the negative electrode active material.
상기 리튬이차전지의 음극활물질로는 탄소계, 규소계, 주석계, 전이금속 산화물 등이 주로 연구개발되고 있다. 그런데 현재까지 개발된 음극활물질은 용량, 초기 충/방전 효율, 팽창율 및 수명 특성이 만족할만한 수준에 도달하지 못하여 개선의 여지가 많다.Carbon-based, silicon-based, tin-based, transition metal oxides, etc. are mainly researched and developed as negative electrode active materials of the lithium secondary battery. However, the negative electrode active material developed so far has a lot of room for improvement as the capacity, initial charge/discharge efficiency, expansion rate, and life characteristics do not reach satisfactory levels.
특히 4족 반도체 물질에 해당하는 Si, Ge, Sn과 같은 물질은 높은 이론용량을 가지기 때문에 새로운 음극재로 주목받고 있으며, 특히 실리콘은 이론용량이 4,200 mAh/g에 달하는 고용량 성능을 보이며, 탄소계열의 음극재를 대체할 차세대 물질로 주목되고 있다.In particular, materials such as Si, Ge, and Sn, which are Group 4 semiconductor materials, are attracting attention as new anode materials because they have high theoretical capacity.In particular, silicon shows high capacity performance of 4,200 mAh/g, and carbon-based It is drawing attention as a next-generation material to replace the anode material of
그러나, 실리콘의 경우, 실리콘 하나당 리튬이 4.4개까지 들어가 합금(alloy)를 이루면서 높은 용량을 보이나, 이 때문에 약 300 % 이상의 부피 변화를 야기한다. 이러한 부피 변화는 충방전이 계속됨에 따라서 음극활물질의 미분화(pulverization)가 발생하고, 음극활물질이 전류 집전체로부터 전기적 탈리되는 현상을 야기한다. 이러한 전기적 탈락은 전지의 용량 유지율을 현저하게 감소시킨다.However, in the case of silicon, up to 4.4 lithium per silicon is added to form an alloy and shows a high capacity, but this causes a volume change of about 300% or more. This volume change causes pulverization of the negative electrode active material as charging and discharging continues, and causes a phenomenon in which the negative electrode active material is electrically separated from the current collector. This electrical dropout significantly reduces the capacity retention rate of the battery.
이러한 문제를 개선하기 위하여 실리콘을 탄소와 기계적인 밀링 공정으로 복합화하고, 실리콘 입자 표면을 화학증착법(CVD)법을 이용하여 탄소층으로 피복하는 기술도 제안되고 있지만(특허문헌 1), 충/방전시에 동반되는 부피 팽창과 수축을 억제하는 데는 한계가 있다. 반면, 산화규소(SiOx)는 규소에 비하여 용량이 작지만, 탄소계 음극용량(약 350 mAh/g) 대비 수배 이상으로 높은 용량(약 1500 mAh/g)을 갖고 있으며, 이산화규소 매트릭스에 실리콘 나노 결정이 균일하게 분산된 구조로 다른 실리콘계 소재에 비하여 부피팽창율과 수명(용량유지율) 특성이 획기적으로 향상된 소재로 각광을 받고 있다.In order to improve this problem, a technique of compounding silicon with carbon by a mechanical milling process and coating the surface of silicon particles with a carbon layer using a chemical vapor deposition method (CVD) is also proposed (Patent Document 1), but charging/discharging There is a limit to suppressing volume expansion and contraction accompanying poetry. On the other hand, silicon oxide (SiOx) has a smaller capacity than silicon, but has a capacity (about 1500 mAh/g) several times higher than that of a carbon-based cathode capacity (about 350 mAh/g), and silicon nanocrystals in a silicon dioxide matrix With this uniformly dispersed structure, it has been in the spotlight as a material with significantly improved volume expansion and life (capacity retention) characteristics compared to other silicon-based materials.
그러나, 이렇게 용량과 수명 특성이 우수한 산화규소는, 초기 충전시에 리튬과 산화규소가 반응하여 리튬산화물(산화리튬 및 리튬규산염 등을 포함)이 생성되는데, 생성된 리튬산화물은 방전시에 가역적으로 양극으로 돌아오지 못하게 된다. 따라서, 이러한 비가역 반응에 의해 리튬이 손실되어 초기 충/방전 효율(ICE)은 75 % 이하로 떨어지게 되므로, 이차전지를 설계하는데 있어서 양극의 용량을 과잉으로 필요하게 되어, 실제 전지에서는 음극이 갖는 단위 질량당의 고용량을 상쇄하게 되는 문제가 있었다.However, in silicon oxide having excellent capacity and lifespan characteristics, lithium and silicon oxide react during initial charging to generate lithium oxide (including lithium oxide and lithium silicate), and the generated lithium oxide is reversibly It will not return to the positive pole. Therefore, lithium is lost due to this irreversible reaction, so that the initial charge/discharge efficiency (ICE) falls below 75%, so that the capacity of the positive electrode is excessively required in designing a secondary battery. There was a problem of offsetting the high capacity per mass.
산화규소(SiO x)의 초기 충/방전 효율을 향상시키기 위한 방법으로, SiO x를 금속 리튬 분말과 반응시켜 Si-SiO x-Li계 복합체를 제조하는 방법(특허문헌 2)이 있는데, 이러한 방법에 의해서는 초기 효율이 향상되지만 전지용량이 감소하고 전극 제작시의 페이스트의 안정성이 떨어지며 취급상의 어려움으로 인하여 공업적인 생산이 어렵다는 문제가 있다.As a method for improving the initial charging/discharging efficiency of silicon oxide (SiO x ), there is a method of preparing a Si-SiO x -Li-based composite by reacting SiO x with metal lithium powder (Patent Document 2). By this, the initial efficiency is improved, but there is a problem that the battery capacity is reduced, the stability of the paste at the time of electrode manufacturing is poor, and industrial production is difficult due to difficulty in handling.
이와 같이 전극 제작시의 안정성을 향상시키기 위하여 SiO x와 마그네슘 화합물을 혼합하여 가열하는 방법으로 규소-규소산화물 복합체를 통해 초기 충/방전 효율을 높이는 방법이 제안되고 있다. In order to improve the stability during electrode fabrication as described above, a method of increasing initial charging/discharging efficiency through a silicon-silicon oxide composite has been proposed as a method of mixing and heating SiO x and a magnesium compound.
특허문헌 3에서는 SiO x와 질산마그네슘(Mg(NO 3) 2)을 반응시켜 Si-SiO 2-Mg 2SiO 4-탄소계 복합재를 제조하였지만, 방전용량이 900 mAh/g, 초기 충/방전효율이 73 %로 낮게 나타났다. 이것은 마그네슘 전구체로 질산마그네슘을 사용하므로써 SiO x와의 반응에서 비정질 SiO 2와 MgO가 다량으로 함유되어 비가역 반응이 억제되지 못하고 충/방전 용량도 기대 이하로 낮게 발현되는 것으로 볼 수 있다.In Patent Document 3, SiO x and magnesium nitrate (Mg(NO 3 ) 2 ) were reacted to prepare a Si-SiO 2 -Mg 2 SiO 4 -carbon-based composite, but the discharge capacity was 900 mAh/g, and the initial charging/discharging efficiency It appeared as low as 73%. This can be seen that the use of magnesium nitrate as a magnesium precursor contains a large amount of amorphous SiO 2 and MgO in the reaction with SiO x , so that irreversible reactions cannot be suppressed and the charge/discharge capacity is expressed lower than expected.
또한, SiO x의 비가역을 감소시키기 위하여 SiO x 분말을 수소화마그네슘(MgH 2) 또는 수소화칼슘(CaH 2)과 반응시켜 마그네슘 또는 칼슘이 함유된 규소-규소산화물 복합체를 제조하는 방법(특허문헌 4)이 보고되고 있다. 이러한 방법으로는 SiO x 분말과 MgH 2 또는 CaH 2의 반응시에 산소의 혼입이 저감되지만 국부적인 발열반응에 의해 실리콘 결정 크기가 급격히 성장하고 Mg 또는 Ca가 불균일하게 분포되므로 SiO x 대비 용량유지율이 떨어지는 것으로 나타났다.In addition, in order to reduce the irreversibility of SiO x , the SiO x powder is reacted with magnesium hydride (MgH 2 ) or calcium hydride (CaH 2 ) to prepare a silicon-silicon oxide composite containing magnesium or calcium (Patent Document 4) Is being reported. With this method, the incorporation of oxygen is reduced during the reaction of SiO x powder and MgH 2 or CaH 2 , but the silicon crystal size rapidly grows due to the local exothermic reaction and Mg or Ca is distributed unevenly, so the capacity retention rate compared to SiO x is reduced. Appeared to fall.
음극활물질로 리튬이 삽입 및 이탈할 수 있는 인조 흑연, 천연 흑연 및 하드 카본을 포함한 다양한 형태의 탄소계 재료가 적용되었다. 상기 탄소계 재료 중 인조 흑연 또는 천연 흑연과 같은 흑연은 리튬 대비 방전 전압이 -0.2 V로 낮아 흑연을 음극활물질로 사용한 전지는 3.6 V의 높은 방전 전압을 나타내 리튬이차전지의 에너지 밀도면에서 바람직하고, 또한 뛰어난 가역성에 의해 리튬이차전지의 수명을 보장하기 위해 가장 널리 이용되고 있다. 그러나, 흑연을 활물질로 극판을 제조할 때 극판 밀도가 낮아져 극판의 단위 부피 당 에너지 밀도면에서 용량이 낮은 문제가 있다. 또한, 높은 방전 전압에 의해 흑연과 유기 전해액과의 부반응이 발생하기 쉬워 전지의 오동작 및 과충전 등에 의한 발화 혹은 폭발의 위험이 있다.Various types of carbon-based materials, including artificial graphite, natural graphite, and hard carbon, through which lithium can be inserted and released as a negative electrode active material, have been applied. Among the carbon-based materials, graphite such as artificial graphite or natural graphite has a discharge voltage of -0.2 V compared to lithium, and a battery using graphite as a negative electrode active material exhibits a high discharge voltage of 3.6 V, which is preferable in terms of energy density of a lithium secondary battery. Also, it is most widely used to guarantee the life of a lithium secondary battery due to its excellent reversibility. However, when manufacturing an electrode plate using graphite as an active material, the density of the electrode plate is lowered, so that the capacity is low in terms of energy density per unit volume of the electrode plate. In addition, a side reaction between graphite and an organic electrolyte is likely to occur due to a high discharge voltage, and there is a risk of ignition or explosion due to malfunction of the battery or overcharging.
이러한 문제를 해결하기 위해 산화물 음극활물질이 최근 개발되고 있다. 예를 들어, 비정질 주석 산화물 음극활물질은 질량이 800 mAh/g의 높은 용량을 가진다. 그러나, 이 주석 산화물은 초기 비가역 용량이 50 % 정도인 치명적인 문제가 있고, 또한 충/방전에 의해 주석 산화물 중 일부가 산화물에서 주석 금속으로 환원되는 등 부수적인 문제도 생겨 이차전지의 사용이 더 어려워지고 있다.In order to solve this problem, oxide anode active materials have been recently developed. For example, the amorphous tin oxide negative electrode active material has a high capacity of 800 mAh/g in mass. However, this tin oxide has a fatal problem with an initial irreversible capacity of about 50%, and also has ancillary problems such as reduction of some of the tin oxide from oxide to tin metal by charging/discharging, making it more difficult to use a secondary battery. Is losing.
다른 산화물 음극으로, 특허문헌 5에는 Li aMg bVO c(0.5≤a≤3, 0.12≤b≤2, 2≤2c-a-2b≤5)의 음극활물질이 기재되어 있다.As another oxide negative electrode, Patent Document 5 describes a negative electrode active material of Li a Mg b VO c (0.5≦a≦3, 0.12≦ b ≦2, 2≦2c-a-2b≦5).
그러나, 아직 산화물 음극으로는 만족할만한 전지 성능을 가지지 않고, 이에 대한 연구가 계속 진행중이다However, it does not yet have satisfactory battery performance as an oxide anode, and research on this is ongoing.
특허문헌 6에는 초미세화된 규소상 입자 및 상기 규소상 입자를 포함하는 산화물로 구성된 복합체 및 탄소 재료를 포함하는 리튬이차전지용 음극활물질이 기재되어 있다. 상기 방법은 메카노케미칼(mechano chemical) 공정을 통해 혼합 또는 열역학적 반응을 거쳐 규소산화물을 환원하여 초미세 규소입자 및 이를 둘러싼 산화물로 구성된 복합체를 제조하고 있다. 그러나, 이 방법은 출발 물질의 규소산화물(SiO x)이 반응을 통해 완전히 규소 상에 환원하는 것으로, 이 경우 초기 효율에 바람직한 영향을 미칠 수 있지만, 활물질의 팽창과 이에 따른 기계적 열화가 상대적으로 크기 때문에 수명에 악영향을 미치는 문제를 일으킨다.Patent Document 6 discloses a negative electrode active material for a lithium secondary battery comprising a carbon material and a composite composed of ultrafine silicon-like particles and oxides containing the silicon-like particles. In the above method, silicon oxide is reduced through mixing or thermodynamic reaction through a mechano chemical process to prepare a composite composed of ultrafine silicon particles and oxides surrounding the silicon oxide. However, in this method, the silicon oxide (SiO x ) of the starting material is completely reduced to the silicon phase through a reaction, and in this case, it may have a favorable effect on the initial efficiency, but the expansion of the active material and the resulting mechanical deterioration are relatively large. Because of this, it causes a problem that adversely affects the lifespan.
특허 문헌 7에는 규소상 이산화규소 및 M yO 금속산화물(상기 M은 산소와 결합을 형성하는 형성 자유에너지가 -900 kJ/mol 내지 -2000 kJ/mol의 금속이며, 상기 M의 산화 숫자를 x로 할 때, x × y = 2를 충족)을 포함하는 나노복합체가 게시되어 있지만, 본 발명과 같이 규소를 포함하는 규산마그네슘 결정이 아니기 때문에 충/방전 용량 및 초기 효율을 향상시킬 수 있을 것으로 기대할 수 없다. 그러나, 본 발명은 초기 충/방전 효율을 높이고, 용량 유지율이 향상된 비수 전해질 리튬이차전지를 제조하는 것을 특징으로 하고 있다.Patent Document 7 discloses silicon dioxide and M y O metal oxide (the M is a metal having a formation free energy of -900 kJ/mol to -2000 kJ/mol to form a bond with oxygen, and the oxidation number of M is x When x × y = 2), a nanocomposite is published, but it is not a magnesium silicate crystal containing silicon as in the present invention, so it is expected that charging/discharging capacity and initial efficiency can be improved. Can't. However, the present invention is characterized by manufacturing a non-aqueous electrolyte lithium secondary battery with improved initial charging/discharging efficiency and improved capacity retention.
특허문헌 8에는 하기 화학식으로 표시되는 규소계 화합물과 탄소 물질을 포함하는 리튬이차전지용 음극활물질이 기재되어 있고, t = (산소) / {(규소) + (마그네슘)}를 계산 하면 0.5 ~ 1.5 의 범위인 것으로 추정된다.Patent Document 8 describes a negative electrode active material for a lithium secondary battery containing a silicon-based compound and a carbon material represented by the following formula, and when t = (oxygen) / {(silicon) + (magnesium)} is calculated, the value of 0.5 to 1.5 It is estimated to be a range.
Si (1-y)M yO 1+x Si (1-y) M y O 1+x
상기 화학식에서, 0 ≤ y ≤ 1, -0.5 ≤ x ≤ 0.5 (몰비), M은 Mg, Ca 임 In the above formula, 0 ≤ y ≤ 1, -0.5 ≤ x ≤ 0.5 (molar ratio), M is Mg, Ca
한편, 후술하는 바와 같이 본 발명은 마그네슘 산화물 결정으로 MgSiO 3과 Mg 2SiO 4을 포함하고 있지만, 특허문헌 8의 발명에 기재된 화학식 Si (1-y)M yO 1+x 에서 x의 범위가 -0.5 ≤ x ≤ 0.5 (몰비)로 되어 있으며, x = 3과 4의 범위가 포함되어 있지 않아, MgSiO 3과 Mg 2SiO 4가 포함되고 있지 않기 때문에, 본 발명과는 크게 다른 것이다.On the other hand, as described later, the present invention includes MgSiO 3 and Mg 2 SiO 4 as magnesium oxide crystals, but the range of x in the formula Si (1-y) M y O 1+x described in the invention of Patent Document 8 is -0.5≦x≦0.5 (molar ratio), and since the range of x=3 and 4 is not included, and MgSiO 3 and Mg 2 SiO 4 are not included, it is significantly different from the present invention.
특허문헌 8에는 음극활물질을 구성하는 규소계 화합물의 제조공정을 설명하고 있다. 우선, SiO 2와 Si의 혼합물에 M 함유 화합물 (M은 Mg, Ca 또는 이들의 혼합물)을 첨가하여 함께 열처리 후 Si (1-y)M yO 1+x 를 얻을 수 있다.Patent Document 8 describes a manufacturing process of a silicon-based compound constituting the negative electrode active material. First, an M-containing compound (M is Mg, Ca, or a mixture thereof) is added to the mixture of SiO 2 and Si, and then heat - treated together to obtain Si (1-y) M y O 1+x .
그러나, 본 발명은 후술하는 바와 같이 규소 복합산화물의 생성이 규소 분말과 이산화규소 분말을 혼합하여 만들어진 규소/이산화규소 원료 분말 혼합체와 금속 마그네슘의 기상 반응, 즉 마그네슘 증기와 산화규소 증기의 반응을 통하여 이루어지며, 균일한 조성의 규소복합산화물을 생성하고 있다.However, in the present invention, as described later, the generation of silicon composite oxide is through a gas phase reaction of a silicon/silicon dioxide raw material powder mixture and metallic magnesium, that is, through a reaction of magnesium vapor and silicon oxide vapor, which is formed by mixing silicon powder and silicon dioxide powder. It is made and produces a silicon composite oxide of a uniform composition.
위와 같이 기상 반응을 통하여 규소복합산화물이 합성되기 때문에, 특허문헌 8에 포함된 고상 반응처럼 Mg가 국부적으로 과잉 혼합되면서 발열 반응에 의해 규소가 급격히 성장 것을 방지된다. 따라서 용량 유지율을 향상시킬 수 있고, 특허문헌 8에 포함된 Si (1-y)M yO 1+x 금속 함유 화합물은 본 발명의 제조방법과 다른 것이기 때문에 초기 충/방전 효율을 높이고, 용량 유지율 등의 특성 향상을 기대할 수 없게 된다. 또한, 특허문헌 8의 실시예는 규소복합산화물 결정을 제작한 기재가 없다.Since the silicon composite oxide is synthesized through the gas phase reaction as described above, Mg is locally excessively mixed as in the solid phase reaction included in Patent Document 8, preventing rapid growth of silicon due to an exothermic reaction. Therefore, the capacity retention rate can be improved, and since the Si (1-y) M y O 1+x metal-containing compound included in Patent Document 8 is different from the manufacturing method of the present invention, the initial charging/discharging efficiency is increased, and the capacity retention rate It becomes impossible to expect improvement of the characteristics of the back. In addition, the Example of Patent Document 8 does not have a description of producing a silicon composite oxide crystal.
본 발명은 상기와 같은 종래 이차전지 음극재용 탄소-규소복합산화물의 문제점을 해결하기 위하여, 규소 산화물을 원료로 하여 규소 입자, MgSiO 3(enstatite) 및 Mg 2SiO 4(forsterite) 결정을 포함하는 규소 복합산화물을 제조하고, 이후, 표면을 탄소 물질로 피복 처리함으로써, 전지의 음극재로 적용시 충/방전 용량과 초기 충/방전 효율 및 용량 유지율이 개선된 리튬이차전지 음극재용 탄소-규소복합산화물 복합체를 제공하는 것을 목적으로 한다.In order to solve the above problems of the conventional carbon-silicon composite oxide for a negative electrode material for secondary batteries, the present invention uses silicon oxide as a raw material and includes silicon particles, MgSiO 3 (enstatite) and Mg 2 SiO 4 (forsterite) crystals. A carbon-silicon composite oxide for a lithium secondary battery negative electrode material with improved charging/discharging capacity, initial charging/discharging efficiency, and capacity retention when applied as a negative electrode material of a battery by preparing a composite oxide and then coating the surface with a carbon material. It aims to provide a composite.
본 발명은 상기와 같은 과제를 해결하기 위하여 규소계 활물질, 산화규소계활물질(SiO X, 0 <x≤2) 및 규산마그네슘 결정을 포함하는 규소복합산화물이며, 표면이 탄소로 코팅되어 있으며, 상기 규소복합산화물을 구성하는 각각의 원소의 원자 비율이 아래 관계식을 만족하는 것인 이차전지 음극재용 탄소-규소복합산화물 복합체를 제공한다.The present invention is a silicon composite oxide comprising a silicon-based active material, a silicon oxide-based active material (SiO X , 0 <x≤2) and a magnesium silicate crystal in order to solve the above problems, the surface is coated with carbon, and the A carbon-silicon composite oxide composite for a secondary battery negative electrode material is provided in which the atomic ratio of each element constituting the silicon composite oxide satisfies the following relationship.
0. 5 <(산소 원자비율) / {(규소 원자비율) + (마그네슘 원자비율)} <1.50 0. 5 <(Atomic ratio of oxygen) / {(Atomic ratio of silicon) + (Atomic ratio of magnesium)} <1.50
본 발명은 상기와 같은 종래의 이차전지의 음극재용 규소 복합산화물의 문제점을 해결하기 위해, 규소계 활물질, 산화규소계 활물질 (SiO X, 0<x≤2)및 규산마그네슘 결정을 포함 규소복합산화물이며, 상기 규소복합산화물의 표면이 탄소로 균일하게 코팅되어 있으며, 탄소-규소복합산화물의 각각의 구성 원소의 원자 비율이 0.5 < (산소 원자비율) / (규소 원자비율) + (마그네슘 원자비율) <1.50 의 범위를 만족하는 것을 특징으로 한다. The present invention is a silicon composite oxide including a silicon-based active material, a silicon oxide-based active material (SiO X, 0<x≤2), and a magnesium silicate crystal in order to solve the problems of the silicon composite oxide for negative electrode material of the conventional secondary battery as described above. And the surface of the silicon composite oxide is uniformly coated with carbon, and the atomic ratio of each constituent element of the carbon-silicon composite oxide is 0.5 <(oxygen atomic ratio) / (silicon atomic ratio) + (magnesium atomic ratio) It is characterized by satisfying the range of <1.50.
본 발명에 의한 이차전지의 음극재용 탄소-규소복합산화물에 있어서,　(산소 원자비율) / {(규소 원자비율) + (마그네슘 원자비율)}의 범위는 0.5 내지 1.05가 바람직하고, 0.7 내지 1.00 인 것이 보다 바람직하다. (산소 원자비율) / {( 규소 원자비율) + (마그네슘 원자비율)}의 범위가 1.50을 초과하는 경우에는 리튬과의 반응시 손실 용량이 차지하는 부분이 증가하고 초기 효율을 저하시킬 우려가 있어 바람직하지 않다. (산소 원자비율) / {(규소 원자비율) + (마그네슘 원자비율)}의 범위가 0.5 미만에서는 초기 효율이 저하되어 바람직하지 않다. In the carbon-silicon composite oxide for an anode material of a secondary battery according to the present invention, the range of 　(oxygen atomic ratio) / {(silicon atomic ratio) + (magnesium atomic ratio)} is preferably 0.5 to 1.05, and 0.7 to 1.00. It is more preferable. When the range of (oxygen atomic ratio) / {(silicon atomic ratio) + (magnesium atomic ratio)} exceeds 1.50, the portion occupied by the loss capacity during the reaction with lithium increases and the initial efficiency may be deteriorated. Not. If the range of (oxygen atomic ratio) / {(silicon atomic ratio) + (magnesium atomic ratio)} is less than 0.5, initial efficiency is lowered, which is not preferable.
본 발명에 있어서, (산소 원자비율) / {(규소 원자비율) + (마그네슘 원자비율)}의 비율을 상기 범위로 최적화하는 경우 리튬이 안정적으로 초기 비가역 반응을 억제하는 효과와 리튬과의 반응시 손실 용량이 차지하는 부분이 증가하고 초기 효율을 저하시키지 않는 효과가 나타난다. In the present invention, when the ratio of (oxygen atomic ratio) / {(silicon atomic ratio) + (magnesium atomic ratio)} is optimized within the above range, the effect of stably suppressing the initial irreversible reaction and the reaction with lithium The portion occupied by the loss capacity increases and the effect of not lowering the initial efficiency is exhibited.
본 발명에서는, Si/SiO 2 원료 분말 혼합체와 마그네슘을 함께 가열시켜 증발된 입자들의 균일한 기상반응으로 규소복합산화물이 합성되며, 고상반응에서 마그네슘이 국부적으로 과잉 혼합되면서 (산소 원자비율) / {(규소 원자비율) + (마그네슘 원자비율)}이 일정 범위로 유지되면서 일어나는 발열 반응에 의해 규소가 급격히 성장하는 것을 방지하여 용량 유지율을 향상시키는 것이 가능하다.In the present invention, a silicon composite oxide is synthesized by a uniform gas phase reaction of the evaporated particles by heating the Si/SiO 2 raw material powder mixture and magnesium together, and while the magnesium is locally excessively mixed in the solid phase reaction (oxygen atomic ratio) / { It is possible to improve the capacity retention rate by preventing rapid growth of silicon due to an exothermic reaction that occurs while (silicon atomic ratio) + (magnesium atomic ratio)} is maintained within a certain range.
본 발명에 의한 이차 전지의 음극재용 규소복합산화물에 있어서, (규소 원자비율) /(마그네슘 원자비율)}의 범위는 2.0 내지 25.0의 범위가 바람직하다. In the silicon composite oxide for a negative electrode material of a secondary battery according to the present invention, the range of (silicon atomic ratio) /(magnesium atomic ratio)} is preferably in the range of 2.0 to 25.0.
본 발명은 규소 분말과 이산화규소 분말을 혼합한 원료 분말 혼합체와 금속 마그네슘을 반응시켜 규소복합산화물을 얻은 후에 얻어진 규소복합산화물의 표면에 탄소 피막을 형성한다. 따라서 탄소 피막 중에 마그네슘 또는 그 산화물 성분을 포함하지 않는 것을 특징으로 한다. The present invention forms a carbon film on the surface of the silicon composite oxide obtained after reacting a raw material powder mixture obtained by mixing silicon powder and silicon dioxide powder with metal magnesium to obtain a silicon composite oxide. Therefore, it is characterized in that the carbon film does not contain magnesium or an oxide component thereof.
또한, 본 발명은 원료 분말 혼합체 및 금속 마그네슘을 가열하여 반응기 내부의 기판에 증착시켜 입자의 균일한 기상 반응에서 규소복합산화물을 합성함으로써 고상 반응처럼 마그네슘이 과잉 혼합되면서 일어나는 발열 반응으로 규소가 급격하게 성장하는 것을 방지하는 것이 특징이다.In addition, the present invention synthesizes silicon composite oxide in a uniform gas phase reaction of particles by heating a raw material powder mixture and metal magnesium to deposit on a substrate inside the reactor, thereby causing an exothermic reaction that occurs when magnesium is excessively mixed like a solid-phase reaction. It is characterized by preventing growth.
본 발명에서 규소계 활물질로 규소를 포함한다. 규소상이 리튬을 충/방전하기 때문에, 규소상이 존재하지 않으면 배터리 용량이 발현하기 어렵기 때문이다. 규소상은 결정질에서 비정질로도 좋지만, 충/방전시의 팽창 수축이 작고, 배터리 성능이 높아지므로 비정질 또는 이에 가까운 상이 바람직하다.In the present invention, silicon is included as a silicon-based active material. This is because since the silicon phase charges/discharges lithium, it is difficult to express the battery capacity if the silicon phase does not exist. The silicon phase may be from crystalline to amorphous, but since the expansion and contraction during charging/discharging is small and battery performance is high, an amorphous or close phase is preferable.
종래 산화규소계 활물질은 (SiO X, 0<x≤2)로 표기되고 X선 회절 분석시 수 nm 내지 수십 nm 정도의 비정질 규소가 산화 규소 중에 미세 분산되어 있는 구조로 제조된다. 따라서 배터리 용량은 규소에 비해 작지만, 탄소와 비교하면 질량 기준으로 5 내지 6 배 높고, 나아가서는 체적 팽창도 작고, 음극할물질로 사용하기 쉽다. 그러나, 이러한 산화규소는 가역 용량이 크고, 초기 효율이 70 % 정도로 매우 낮기 때문에 실제로 전지를 제작한 경우는 양극의 전지 용량을 과도하게 요구하고 활물질당 5 내지 6 배 용량 증가분에 걸 맞는 배터리 용량의 증가를 기대할 수 없었다. 산화규소의 실용상의 문제점은 크게 초기 효율이 낮은 점에 있었다. The conventional silicon oxide-based active material is expressed as (SiO X, 0<x≤2), and is prepared in a structure in which amorphous silicon of several nm to tens of nm is finely dispersed in silicon oxide when analyzed by X-ray diffraction. Therefore, the battery capacity is smaller than that of silicon, but is 5 to 6 times higher on a mass basis compared to carbon, and further, the volume expansion is small, and it is easy to use as a negative electrode material. However, since silicon oxide has a large reversible capacity and a very low initial efficiency of about 70%, when a battery is actually manufactured, the battery capacity of the positive electrode is excessively demanded, and the battery capacity corresponding to a 5 to 6 times increase in capacity per active material. Could not expect an increase. The practical problem of silicon oxide was that the initial efficiency was largely low.
일반적으로, 산화규소계 활물질은 비가역 용량이 크고 수명이 짧아 고율 충 방전 고율이 좋지 않기 때문에 리튬이차전지용 음극활물질로 사용하기에 적합하지 않다. 이는 충/방전시 구조적 안정성이 낮기 때문에 리튬 원자의 확산 속도가 낮은 때문이다.In general, a silicon oxide-based active material is not suitable for use as a negative electrode active material for a lithium secondary battery because its irreversible capacity is large and its life is short, and the high rate charging and discharging rate is not good. This is because the diffusion rate of lithium atoms is low because the structural stability during charging/discharging is low.
한편, SiOx(0 <x≤ 1)의 경우, 규소 원자가 산소 원자와 공유 결합하고 있다. 규소 원자가 리튬 원자와 결합하려면 규소 원자와 산소 원자와 공유 결합을 끊어야 하지만, 공유 결합을 끊을 수 있는 에너지가 부족하기 때문에 리튬 원자가 삽입 되어도 SiOx(0 <x≤ 1) 구조는 파괴되지 않는다. 즉, SiOx(0 <x≤ 1)과 리튬 원자와 반응은 SiOx(0 <x≤ 1) 구조를 유지하면서 진행하여 얻기 때문에, 사이클 수명과 용량이 증가될 수 있다.On the other hand, in the case of SiOx (0 <x ≤ 1), a silicon atom is covalently bonded to an oxygen atom. In order for a silicon atom to bond with a lithium atom, it is necessary to break a covalent bond with a silicon atom and an oxygen atom, but since the energy to break the covalent bond is insufficient, the SiOx (0 <x ≤ 1) structure is not destroyed even if a lithium atom is inserted. That is, since the reaction with SiOx (0 <x≤ 1) and lithium atoms proceeds while maintaining the SiOx (0 <x≤ 1) structure, the cycle life and capacity can be increased.
산화규소계 활물질은 절연체이기 때문에 어떠한 수단으로 도전성을 부여할 필요가 있다. 상기 전도성을 부여하기 위해 규소복합산화물의 표면을 탄소로 코팅하는 방법으로는 규소복합산화물을 유기물 가스 및/또는 증기 중에서 화학 증착(CVD) 방법이 바람직하며, 열처리시 반응기 내에 유기물 가스 및/또는 증기를 도입하여 효율적으로 할 수 있다.Since the silicon oxide-based active material is an insulator, it is necessary to impart conductivity by some means. As a method of coating the surface of the silicon composite oxide with carbon in order to impart the conductivity, a chemical vapor deposition (CVD) method of the silicon composite oxide in organic gas and/or vapor is preferable, and the organic gas and/or vapor in the reactor during heat treatment You can do it efficiently by introducing
구체적으로는 전도성에 영향을 미치는 것은 탄소 코팅의 양뿐만 아니라 그 피막의 균일성도 중요하다. 예를 들어, 충분한 탄소량을 얻을 수 있어도, 피막이 고르지 않고, 산화규소계 활물질의 표면이 부분적으로 노출되어 있으면, 그 부분은 절연되어 충/방전 용량과 사이클 특성에 악영향을 미친다.Specifically, it is not only the amount of carbon coating that affects the conductivity but also the uniformity of the film. For example, even if a sufficient amount of carbon can be obtained, if the film is uneven and the surface of the silicon oxide-based active material is partially exposed, the portion is insulated and adversely affects charge/discharge capacity and cycle characteristics.
또한, 규소계 활물질, 즉 규소 입자가 산화규소계 활물질 중에 분산된 구조를 갖는 산화규소계 활물질은 산화규소인 것이 바람직하다. 또한, 투과전자현미경에 의해 규소 입자 결정이 무정형의 산화규소계 활물질에 분산되어 있는 것을 확인할 수 있다. 산화규소계 활물질은 화학식 SiOx(0 <x≤2)로 표시되는 산화규소 및 규소 산화물을 들 수 있다. 상기 산화규소는 이산화규소와 금속 규소의 혼합물을 가열하여 생성된 산화규소 가스를 냉각, 석출시키는 것 등으로 얻을 수 있다. 특히 SiOx(0.5 ≤ x <1.6)로 표시되는 산화규소 입자인 것이 바람직하다.Further, it is preferable that the silicon-based active material, that is, the silicon oxide-based active material having a structure in which silicon particles are dispersed in the silicon oxide-based active material, is silicon oxide. Further, it can be confirmed that the silicon particle crystals are dispersed in an amorphous silicon oxide-based active material by a transmission electron microscope. The silicon oxide-based active material may include silicon oxide and silicon oxide represented by the formula SiOx (0 <x≦2). The silicon oxide can be obtained by heating a mixture of silicon dioxide and silicon metal to cool and precipitate a silicon oxide gas generated. In particular, it is preferable that it is a silicon oxide particle represented by SiOx (0.5≦x<1.6).
산화규소는 비정질(Amorphous)인 것이 바람직하다. 상기 산화규소가 무정형 (Amorphous)인 경우에는 리튬의 삽입 및 이탈하여 상기 규소를 포함하는 산화규소의 부피가 변화하는 경우에도, 상기 산화규소의 미분화(pulverization)을 방지하거나 완화할 수 있으며, 상기 규소와 전해질과의 부반응을 방지 또는 감소시킬 수 있다.Silicon oxide is preferably amorphous. When the silicon oxide is amorphous, the pulverization of the silicon oxide can be prevented or alleviated, even when the volume of the silicon oxide including the silicon is changed due to the insertion and removal of lithium, and the silicon It is possible to prevent or reduce side reactions between the and electrolyte.
산화규소계 활물질은 비정질에서 방전시 리튬이온과 비가역 반응을 일으켜 Li-Si-O 또는 Si + Li 2O를 형성한다. 따라서, 산화규소계 활물질의 함량이 높을수록 초기 비가역 반응이 증가하여 초기 효율이 저하되는 문제가 있다.The silicon oxide-based active material causes an irreversible reaction with lithium ions when discharged in amorphous to form Li-Si-O or Si + Li 2 O. Therefore, as the content of the silicon oxide-based active material increases, there is a problem that the initial irreversible reaction increases and the initial efficiency decreases.
따라서, 상기 산화규소계 활물질은 규소복합산화물에 5 내지 45 몰%로 포함되는 것이 바람직하다. 산화규소계 활물질의 함량이 5 몰% 미만의 경우 부피 팽창 및 수명 특성이 나빠져 바람직하지 않으며, 45 몰%를 초과 할 경우 초기 비가역 반응이 증가하여 바람직하지 않다.Therefore, the silicon oxide-based active material is preferably contained in an amount of 5 to 45 mol% in the silicon composite oxide. When the content of the silicon oxide-based active material is less than 5 mol%, volume expansion and lifespan characteristics are deteriorated, which is not preferable, and when it exceeds 45 mol%, the initial irreversible reaction increases, which is not preferable.
또한, 이산화규소(SiO 2)는 리튬과 반응할 때, 리튬규산염이 생성되는 비가역 반응을 일으켜 초기 효율을 저하시키는 원인이 된다. 또한, 금속 마그네슘 및 MgSi 합금은 활성으로 반응성이 높고, 전지 제작시에 부재와 반응하는 등 취급을 어렵게 한다. 따라서, 마그네슘 도핑 산화규소계 음극 재료는 이산화규소와 금속 마그네슘, MgSi 합금이 생기지 않도록 구성을 엄격하게 관리하고 있지만 실제로는 원소 농도 분포의 불균일에 기인하여 이산화규소 및 금속 마그네슘, MgSi 합금이 발생할 위험이 있다.In addition, when silicon dioxide (SiO 2 ) reacts with lithium, it causes an irreversible reaction in which lithium silicate is generated, thereby lowering initial efficiency. In addition, metal magnesium and MgSi alloys are highly reactive due to activity, and they react with members during battery fabrication, making handling difficult. Therefore, the composition of magnesium-doped silicon oxide-based negative electrode materials is strictly controlled so that silicon dioxide, metallic magnesium, and MgSi alloys do not occur, but in reality there is a risk of occurrence of silicon dioxide, metallic magnesium, and MgSi alloys due to uneven element concentration distribution. have.
이산화규소를 포함하지 않는 것이 바람직한데, 그 이유는 규소 삽입시 리튬규산염 생성이 억제되어 초기 효율이 향상한다. 이산화규소를 포함하는 경우, 리튬과 반응하여 리튬규산염이 생성되어 비가역 반응이 일어나, 초기 효율이 저하된다.It is preferable not to include silicon dioxide, because the formation of lithium silicate is suppressed when silicon is inserted, thereby improving initial efficiency. When silicon dioxide is included, lithium silicate is produced by reacting with lithium, resulting in an irreversible reaction, resulting in lower initial efficiency.
본 발명의 탄소층을 형성하는 과정은 제작한 규소복합산화물을 메탄, 에탄, 프로판, 부탄, 에틸렌, 프로필렌, 부타디엔, 메탄올, 에탄올, 프로판올 아세틸렌, 벤젠 및 톨루엔으로부터 선택되는 하나 또는 이들의 조합을 이용하여 600 내지 1200 ℃에서 가스 상태로 반응시키는 것을 특징으로 하며, 아래에서 상세하게 설명한다.In the process of forming the carbon layer of the present invention, one selected from methane, ethane, propane, butane, ethylene, propylene, butadiene, methanol, ethanol, propanol acetylene, benzene and toluene, or a combination thereof is used to form the silicon composite oxide. It is characterized by reacting in a gaseous state at 600 to 1200° C., which will be described in detail below.
본 발명에 의한 이차 전지의 음극재료용 규소복합산화물에 있어서,　탄소층은 그래핀, 환원된 산화 그래핀 또는/및 탄소 나노 섬유를 주성분으로 형성되는 것이 바람직하며, 아래의 화학식1, 화학식2 및 화학식 3으로 표시되는 탄소원 반응 가스, 반응 시간 및 반응 온도에 의해 변화된다. In the silicon composite oxide for a negative electrode material of a secondary battery according to the present invention, 　 the carbon layer is preferably formed of graphene, reduced graphene oxide or/and carbon nanofibers as a main component, and the following Chemical Formulas 1, 2 and It changes depending on the carbon source reaction gas represented by Chemical Formula 3, the reaction time, and the reaction temperature.
[화학식 1] C nH (2n+2-A)[OH] A [Formula 1] C n H (2n+2-A) [OH] A
상기 화학식 1 중, n은 1 내지 20의 정수, A는 0 또는 1이며,In Formula 1, n is an integer of 1 to 20, A is 0 or 1,
[화학식 2] C nH (2n-A) [Formula 2] C n H (2n-A)
상기 화학식 2 중, n은 2 내지 6의 정수이고, A는 0 또는 1이며In Formula 2, n is an integer of 2 to 6, A is 0 or 1,
[화학식 3] C xH yO z [Chemical Formula 3] C x H y O z
상기 화학식 3 중, x는 0 또는 1 내지 20의 정수이고, y는 0 또는 1 내지 20의 정수이고, z는 0, 1 또는 2이다. In Formula 3, x is 0 or an integer of 1 to 20, y is 0 or an integer of 1 to 20, and z is 0, 1 or 2.
상기 화학식 1로 표시되는 화합물과 화학식 2로 표시되는 화합물은 예를 들면 메탄, 에탄, 프로판, 부탄, 에틸렌, 프로필렌, 부타디엔, 메탄올, 에탄올, 프로판올로 이루어진 군으로부터 선택된 하나 이상이다. 화학식 3으로 표시되는 산소 함유 가스는 예를 들면, 이산화탄소(CO 2)와 일산화탄소(CO), 수증기(H 20), 벤질알코올이며, 화학식 3으로 표시되는 산소를 함유하지 않는 가스는 예를 들면 아세틸렌, 벤젠, 톨루엔, 자일렌 또는 그 혼합물을 포함한다.The compound represented by Formula 1 and the compound represented by Formula 2 are, for example, at least one selected from the group consisting of methane, ethane, propane, butane, ethylene, propylene, butadiene, methanol, ethanol, and propanol. The oxygen-containing gas represented by Formula 3 is, for example, carbon dioxide (CO 2 ), carbon monoxide (CO), water vapor (H 2 O), and benzyl alcohol, and the gas not containing oxygen represented by Formula 3 is, for example, Acetylene, benzene, toluene, xylene or mixtures thereof.
탄소원 가스 이외에 질소, 헬륨, 아르곤으로 이루어진 군으로부터 선택된 복수의 불활성 가스를 더 포함할 수 있다.In addition to the carbon source gas, a plurality of inert gases selected from the group consisting of nitrogen, helium, and argon may be further included.
상기 산소 함유 가스는 일산화탄소, 이산화탄소, 수증기로 이루어진 군으로부터 선택된 하나 이상일 수 있다.The oxygen-containing gas may be at least one selected from the group consisting of carbon monoxide, carbon dioxide, and water vapor.
상기 가스 혼합물이 수증기를 포함하는 경우에는 얻어진 본 발명에 의한 이차전지의 음극재용 규소복합산화물은 높은 전도성을 나타낼 수 있다. 수증기의 존재하에서 상기 가스 혼합물 사이의 반응에 의해 본 복합체의 표면에 높은 결정성 탄소 피복이 형성되기 때문에 적은 양의 탄소가 코팅되는 경우에도 높은 전도도를 보여줄 수 있는 것으로 추측된다. 상기 가스 혼합물 내의 수증기 함량은 제한되지 않고, 예를 들면, 탄소원 가스 전체 100 부피 %를 기준으로 0.01 내지 10 부피%를 사용하면 바람직하다.When the gas mixture contains water vapor, the obtained silicon composite oxide for a negative electrode material of a secondary battery according to the present invention may exhibit high conductivity. In the presence of water vapor, since a highly crystalline carbon coating is formed on the surface of the composite by the reaction between the gas mixtures, it is assumed that high conductivity can be exhibited even when a small amount of carbon is coated. The water vapor content in the gas mixture is not limited, and for example, it is preferable to use 0.01 to 10% by volume based on 100% by volume of the total carbon source gas.
상기 탄소원 가스는, 예를 들어 메탄; 메탄과 불활성 가스를 포함하는 혼합 가스; 산소 함유 가스; 또는 메탄과 산소 함유 가스를 포함하는 혼합 가스인 것이 있다.The carbon source gas may be, for example, methane; A mixed gas containing methane and an inert gas; Oxygen-containing gas; Alternatively, there may be a mixed gas containing methane and an oxygen-containing gas.
일 실시예에 따른 탄소원가스는 CH 4:CO 2 혼합 기체 또는 CH 4:CO 2:H 2O 혼합 기체일 수 있다. CH 4:CO 2 혼합 기체는 약 1 : 0.20 내지 0.50의 몰비로 제공될 수 있으며, 구체적으로는 약 1 : 0.25 내지 0.45의 몰비로 제공될 수 있으며, 보다 구체적으로 약 1 : 0.30 내지 0.40의 몰비가 바람직하다. The carbon source gas according to an embodiment may be a CH 4 :CO 2 mixed gas or a CH 4 :CO 2 :H 2 O mixed gas. The CH 4 :CO 2 mixed gas may be provided in a molar ratio of about 1: 0.20 to 0.50, and specifically, may be provided in a molar ratio of about 1: 0.25 to 0.45, and more specifically, a molar ratio of about 1: 0.30 to 0.40 Is preferred.
CH 4:CO 2:H 2O 혼합 기체는 약 1 : 0.20 내지 0.50 : 0.01 내지 1.45의 몰비로 제공된다. 구체적으로는 약 1 : 0.25 내지 0.45 : 0.10 내지 1.35의 몰비가 바람직하다. 또한, 약 1 : 0.30 내지 0.40 : 0.50 내지 1.0의 몰비가 바람직하다.The CH 4 :CO 2 :H 2 O mixed gas is provided in a molar ratio of about 1: 0.20 to 0.50: 0.01 to 1.45. Specifically, a molar ratio of about 1: 0.25 to 0.45: 0.10 to 1.35 is preferable. Further, a molar ratio of about 1: 0.30 to 0.40: 0.50 to 1.0 is preferred.
다른 일 실시예에 따른 탄소원가스는 일산화탄소 (C0) 또는 이산화탄소 (CO 2)일 수 있다. 다른 일 실시예에 따른 탄소원가스는 CH 4와 N 2의 혼합 기체이다. CH 4와 N 2 혼합 기체는 약 1 : 0.20 내지 0.50의 몰비로 제공된다. 구체적으로는 약 1 : 0.25 내지 0.45의 몰비가 바람직하다. 보다 바람직하게는 약 1 : 0.30 내지0.40의 몰비이다. 일 실시예에 따른 탄소 소스 가스는 질소와 같은 불활성 가스를 포함하지 않는 경우도 있다.The carbon source gas according to another embodiment may be carbon monoxide (C0) or carbon dioxide (CO 2 ). The carbon source gas according to another embodiment is a mixed gas of CH 4 and N 2 . The mixed gas of CH 4 and N 2 is provided in a molar ratio of about 1: 0.20 to 0.50. Specifically, a molar ratio of about 1: 0.25 to 0.45 is preferred. More preferably, it is a molar ratio of about 1:0.30 to 0.40. The carbon source gas according to an embodiment may not contain an inert gas such as nitrogen.
상기 열처리는 700 내지 1100 ℃, 예를 들면, 700 내지 1000 ℃에서 실시되면 바람직하다.The heat treatment is preferably performed at 700 to 1100 °C, for example, 700 to 1000 °C.
열처리 단계에서의 압력도 제한되지 않고, 열처리 온도, 가스 혼합물의 조성 및 원하는 탄소 코팅의 양 등을 고려하여 선택하면 바람직하다. 열처리시의 압력은 유입되는 가스 혼합물의 양으로 유출하는 가스 혼합물의 양을 조절하여 제어할 수 있다. 예를 들면, 열처리시의 압력은 1atm 이상, 예를 들면, 2 atm 이상, 3 atm 이상, 4 atm 이상, 5 atm 이상 할 수 있지만, 이에 한정되는 것은 아니다.The pressure in the heat treatment step is also not limited, and it is preferable to select it in consideration of the heat treatment temperature, the composition of the gas mixture, and the desired amount of carbon coating. The pressure during the heat treatment can be controlled by adjusting the amount of the gas mixture flowing out to the amount of the gas mixture flowing in. For example, the pressure during heat treatment may be 1 atm or more, for example, 2 atm or more, 3 atm or more, 4 atm or more, 5 atm or more, but is not limited thereto.
열처리 시간은 특별히 제한되지 않고, 열처리 온도, 열처리시의 압력, 가스 혼합물의 조성 및 원하는 탄소 코팅의 양에 따라 적절하게 조정할 수 있다. 예를 들어, 상기 반응 시간은 10 분 내지 100 시간, 구체적으로 30 분 내지 90 시간, 보다 구체적으로는 50 분 내지 40 시간일 수 있지만, 이에 한정되지 않는다. 반응 시간이 길어질수록 형성되는 탄소 피막의 두께가 많아지고, 그에 따라 복합체의 전기적 물성을 향상시킬 수 있다.The heat treatment time is not particularly limited, and may be appropriately adjusted according to the heat treatment temperature, the pressure during heat treatment, the composition of the gas mixture, and the desired amount of carbon coating. For example, the reaction time may be 10 minutes to 100 hours, specifically 30 minutes to 90 hours, more specifically 50 minutes to 40 hours, but is not limited thereto. As the reaction time increases, the thickness of the formed carbon film increases, thereby improving the electrical properties of the composite.
상기 복합체의 제조 방법은 상술한 탄소원 가스의 기상 반응을 통해 비교적 낮은 온도에서도 규소·산화 규소 - 탄소 복합체의 표면 전체에 걸쳐 그래핀 환원 된 산화 그래핀 또는/및 탄소나노섬유를 실질적으로 많이 포함하는 균일한 탄소 피막이 형성되어 있기 때문에 바람직하다. 그리고, 탄소 피막의 제거 반응이 거의 일어나지 않는다.The manufacturing method of the composite includes substantially a large amount of graphene oxide or/and carbon nanofibers reduced by graphene over the entire surface of the silicon-silicon oxide-carbon composite even at a relatively low temperature through the gas phase reaction of the carbon source gas described above. It is preferable because a uniform carbon film is formed. And, the carbon film removal reaction hardly occurs.
또한, 기상 반응을 통해 본 산화물의 표면에 탄소 피막이 균일하게 형성되므로, 높은 결정성을 갖는 탄소 피막을 형성 할 수 있으며, 상기 복합물을 음극 활물질로 사용하는 경우 구조는 변화하지 않고 음극 활물질의 전도도를 향상시킬 수 있다.In addition, since the carbon film is uniformly formed on the surface of the oxide through the gas phase reaction, a carbon film having high crystallinity can be formed. When the composite is used as a negative electrode active material, the structure does not change and the conductivity of the negative electrode active material is reduced. Can be improved.
본 발명은 그래핀, 환원된 산화 그래핀, 또는/및 탄소나노섬유(그래핀 함유 물질 이라 칭함)를 실질적으로 많이 포함하는 탄소 피막이 형성되어 있는 것이 특징이지만, 규소·산화규소-탄소복합체의 상부에 상기 탄소원 가스로 이루어진 반응 가스를 공급하면, 산화규소 및 그 환원 생성물로부터 선택된 재료의 표면에 그래핀 함유 물질이 성장하게 된다. 반응 시간의 경과에 따라 그래핀 함유 물질이 서서히 형성되어 탄소-규소복합산화물 복합체를 얻을 수 있게 된다.The present invention is characterized in that a carbon film containing substantially a large amount of graphene, reduced graphene oxide, or/and carbon nanofibers (referred to as graphene-containing materials) is formed, but the upper part of the silicon-silicon oxide-carbon composite When a reaction gas composed of the carbon source gas is supplied to the graphene-containing material, a graphene-containing material is grown on the surface of a material selected from silicon oxide and its reduction product. As the reaction time elapses, the graphene-containing material is gradually formed to obtain a carbon-silicon composite oxide composite.
본 발명에 의한 이차전지의 음극재용 탄소-규소복합산화물 복합체에 있어서,　그래핀 함유 물질의 구조는 막(layer) 또는 나노 시트(nanosheet) 타입이거나 또는 일부 조각이 혼합된 구조일 수 있다.In the carbon-silicon composite oxide composite for an anode material of a secondary battery according to the present invention, the structure of the graphene-containing material may be a layer or a nanosheet type, or a structure in which some pieces are mixed.
나노 시트는 산화규소 및 그 환원 생성물로부터 선택된 하나 이상의 상부에 그래핀이 불규칙한 상태로 형성된 경우를 나타내고, 막은 산화규소 및 그 환원 생성물로부터 선택된 하나 이상의 상단에 그래핀이 연속적으로 균일하게 형성된 필름의 형태를 말한다. 그리고, 조각은 상술한 나노 시트 또는 필름의 일부가 손상되거나 변형된 경우를 말할 수 있다.The nanosheet represents a case in which graphene is formed in an irregular state on at least one selected from silicon oxide and its reduction products, and the film is in the form of a film in which graphene is continuously and uniformly formed on at least one selected from silicon oxide and its reduction products Say. In addition, the fragment may refer to a case in which a part of the above-described nanosheet or film is damaged or deformed.
본 발명은 본 산화물의 표면에 있는 그래핀 함유 물질의 균일한 코팅을 제공한다. 본 발명에 의한 이차전지의 음극재용 탄소-규소복합산화물 복합체는 규소와 산화규소 표면에 전도성이 우수한 체적 팽창에 유연한 그래핀 함유 물질을 직접 성장시켜 체적 팽창을 억제하고 규소와 산화규소가 분쇄되는 현상을 줄일 수 있다. 그리고, 그래핀에 의해 규소가 전해질과 직접 만날 수 있는 기회를 줄여 SEI(Solid Electrolyte Interface) 계층의 생성을 줄일 수 있다.The present invention provides a uniform coating of the graphene-containing material on the surface of the present oxide. The carbon-silicon composite oxide composite for a negative electrode material of a secondary battery according to the present invention inhibits volume expansion by directly growing a graphene-containing material having excellent conductivity on the surface of silicon and silicon oxide, which is flexible in volume expansion, and silicon and silicon oxide are pulverized. Can be reduced. In addition, it is possible to reduce the generation of a solid electrolyte interface (SEI) layer by reducing the opportunity for silicon to directly meet the electrolyte by graphene.
본 발명은 규소 분말과 이산화규소 분말을 혼합한 원료분말혼합체와 금속 마그네슘을 반응시켜 규소복합산화물을 얻은 후에 얻어진 규소복합산화물의 표면에 탄소 피막을 형성하므로 탄소 피막 중에 마그네슘 또는 그 산화물 성분을 포함하지 않는다. The present invention forms a carbon film on the surface of the silicon composite oxide obtained after reacting a raw material powder mixture of silicon powder and silicon dioxide powder with metal magnesium to obtain a silicon composite oxide, so that magnesium or its oxide component is not included in the carbon film. Does not.
또한, 본 발명은 원료분말혼합체 및 금속 마그네슘을 가열하여 기체상태에서 반응시키고, 반응기 내부의 기판에 증착시켜 입자의 균일한 기상 반응에서 규소복합산화물을 합성하기 때문에 원료분말과 마그네슘이 고르게 반응하며, 고상 반응처럼 마그네슘이 현지에 과잉 혼합되면서 발열 반응으로 규소가 급격하게 성장하는 것을 방지할 수 있으며, 규소의 미세 결정이 규산 마그네슘 중에 분산, 즉 둘러 쌓이는 구조로 형성되며, 충방전에 의한 규소의 팽창 수축을 억제하여 높은 배터리 성능을 얻을 수 있다. In addition, in the present invention, since the raw material powder mixture and the metal magnesium are heated to react in a gaseous state, and deposited on the substrate inside the reactor to synthesize the silicon composite oxide in a uniform gas phase reaction of the particles, the raw material powder and magnesium react evenly, As in the solid-state reaction, magnesium is excessively mixed in the field to prevent rapid growth of silicon due to an exothermic reaction, and microcrystals of silicon are dispersed in magnesium silicate, that is, formed in an enclosed structure, and the expansion of silicon by charging and discharging High battery performance can be obtained by suppressing shrinkage.
본 발명에 따른 음극활물질은 X 선 회절 패턴 분석에서 규소 결정으로 인한 피크가 나타난다고 생각되며, 회절각이 2θ ＞ 28 °범위에서 나타나는 피크는 결정 크기가 2 내지 10 nm 인 규소 결정에 의한 것이다. The anode active material according to the present invention is considered to have a peak due to a silicon crystal in the X-ray diffraction pattern analysis, and the peak appearing in the range of 2θ> 28° is due to a silicon crystal having a crystal size of 2 to 10 nm.
X선 회절(Cu-Kα)에서 2θ = 47.5 °부근을 중심으로 한 Si(220)에 귀속되는 회절선 퍼짐을 바탕으로 쉐러의 식에 의해 구한 규소입자의 미세 결정의 결정자 크기가 2 내지 10 nm 인 것이 바람직하고, 보다 바람직하게는 2 내지 8 nm 인 것이 바람직하다.In X-ray diffraction (Cu-Kα), the crystallite size of the fine crystals of the silicon particles determined by Scherrer's equation based on the spread of the diffraction rays attributed to Si (220) around 2θ = 47.5 ° is 2 to 10 nm It is preferable that it is, and it is more preferable that it is 2-8 nm.
본 발명에 의한 이차전지의 음극재용 규소복합산화물은 규소계 활물질의 규소 입자가 무정형 및/또는 2 내지 10 nm의 입자인 것이 바람직하다. 본 발명에 의한 이차전지의 음극재용 규소복합산화물은 규소의 미세 결정이나 입자가 균일하게 분산되는 것이 바람직하다. In the silicon composite oxide for a negative electrode material of a secondary battery according to the present invention, the silicon particles of the silicon-based active material are preferably amorphous and/or 2 to 10 nm particles. In the silicon composite oxide for a negative electrode material of a secondary battery according to the present invention, it is preferable that fine crystals or particles of silicon are uniformly dispersed.
규소가 완전한 비정질로 혼연일체가 된 상태가 아니기 때문에 충/방전 용량이 작아질 우려가 거의 없고, 규소 미세 결정의 결정자 크기가 10 nm 이하의 것이기 때문에, 규소 입자의 일부가 충/방전에 기여하지 않는 영역이 발생할 가능성이 낮고, 쿨롱 효율의 저하를 확실하게 억제할 수 있다.Since silicon is not completely amorphous and mixed and unified, there is little concern that the charge/discharge capacity will decrease.Since the crystallite size of the silicon microcrystal is less than 10 nm, some of the silicon particles do not contribute to charging/discharging. The possibility of occurrence of a region is low, and a decrease in Coulomb efficiency can be reliably suppressed.
또한, 본 발명에 의한 이차전지의 음극재용 규소복합산화물은 규소가 미립자이므로, 큰 비표면적에 리튬 합금을 형성하여 대량의 파괴를 억제하는 것이 가능하다. 충전 시 규소 입자는 리튬과 반응하여 LiySix(Li 4.2Si 등)를 형성하고, 방전 시 규소 단상에 돌아온다. 또한, 이러한 크기의 규소 미립자이면 비수 전해질을 사용하는 이차전지용 음극활물질로 사용한 경우, 충/방전시의 체적 변화가 억제되어 결정 입계에서의 응력이 완화되기 때문에 높은 초기 효율과 배터리 용량이 유지된다.In addition, since the silicon composite oxide for a negative electrode material of a secondary battery according to the present invention contains silicon particles, it is possible to suppress a large amount of destruction by forming a lithium alloy on a large specific surface area. During charging, silicon particles react with lithium to form LiySix (Li 4.2 Si, etc.), and return to the silicon single phase when discharged. In addition, when silicon fine particles of this size are used as a negative electrode active material for a secondary battery using a non-aqueous electrolyte, the volume change during charging/discharging is suppressed to relieve the stress at the grain boundary, thereby maintaining high initial efficiency and battery capacity.
규소 입자를 더욱 미립화, 즉 비정질 형상이나 결정자 크기를 3 내지 6 nm 정도로 형성되는 경우, 본 복합체의 밀도가 커져 이론 밀도에 접근하고 기공이 크게 감소하게 되어 바람직하다. 이를 통해 매트릭스의 밀도가 증가하고 강도가 강화되어 균열을 방지하기 때문에, 초기 효율 및 사이클 수명의 향상을 도모한다.When the silicon particles are further atomized, that is, an amorphous shape or a crystallite size of about 3 to 6 nm is formed, the density of the present composite increases, approaching the theoretical density, and pores are greatly reduced, which is preferable. Through this, the density of the matrix is increased and the strength is strengthened to prevent cracking, thereby improving initial efficiency and cycle life.
본 발명에 의한 이차 전지의 음극 재료용 규소 복합 산화물은 규소의 결정자 크기는 2 내지 10 nm의 입자인 것이 바람직하다. 규소의 미세 결정이 균일하게 분산되는 것이 바람직하다. 규소 입자의 결정자 크기는 마그네슘의 첨가와 함께 커지는 경향이 있다. 마그네슘 첨가량이 10 중량%를 초과하면 규소의 결정자 크기가 12 내지 15 nm로 커진다. The silicon composite oxide for a negative electrode material of a secondary battery according to the present invention preferably has a crystallite size of 2 to 10 nm. It is preferable that the fine crystals of silicon are uniformly dispersed. The crystallite size of the silicon particles tends to increase with the addition of magnesium. When the amount of magnesium added exceeds 10% by weight, the crystallite size of silicon increases to 12 to 15 nm.
본 발명에 의한 이차전지의 음극재용 규소복합산화물은 규소 입자가 산화규소계 활물질과 규산 마그네슘에 분산된 구조를 갖는다.The silicon composite oxide for a negative electrode material of a secondary battery according to the present invention has a structure in which silicon particles are dispersed in a silicon oxide-based active material and magnesium silicate.
본 발명에 의한 이차전지의 음극재용 탄소-규소복합산화물 복합체에 대한 규소 함유량은 30 내지 80 중량% 인 것이 바람직하다. 또한, 40 내지 70 중량%, 특히 40 내지 60 중량% 인 것이 바람직하다. 30 중량% 미만에서는 리튬 흡장·방출 활물질의 양이 적기 때문에 리튬이온전지의 충/방전 용량이 작아지고, 반대로 80 중량% 보다 많아지면 리튬이온전지의 충/방전 용량은 크게 되지만, 규소상이 많이 석출하고, 충/방전시 전극의 팽창·수축이 너무 커져, 음극활물질 분말이 더욱 미분화하여 사이클 특성이 저하될 우려가 있다.The silicon content of the carbon-silicon composite oxide composite for a negative electrode material of a secondary battery according to the present invention is preferably 30 to 80% by weight. Further, it is preferably 40 to 70% by weight, particularly 40 to 60% by weight. If it is less than 30% by weight, the charge/discharge capacity of the lithium-ion battery decreases because the amount of the lithium occlusion/release active material is small. In addition, during charging/discharging, the expansion and contraction of the electrode becomes too large, so that the negative electrode active material powder is further finely divided, thereby deteriorating the cycle characteristics.
본 발명에 의한 상기 규소복합산화물 전체 100 중량부당 Mg를 2 내지 20 중량부의 비율로 포함할 수 있다. Mg may be included in a ratio of 2 to 20 parts by weight per 100 parts by weight of the total silicon composite oxide according to the present invention.
본 발명에 의한 음극활물질은 X선 회절 패턴 분석시 MgSiO 3(enstatite)결정이 회절각 28 °< 2θ < 29 °범위 내에서 규소 결정에 귀속되는 피크가 나타나고, 회절각 30.5 ° ＜2θ < 31.5 °범위 내에서 MgSiO 3결정에 귀속되는 피크가 나타날 수 있다.In the negative electrode active material according to the present invention, when an X-ray diffraction pattern is analyzed, the MgSiO 3 (enstatite) crystal exhibits a peak attributable to the silicon crystal within a diffraction angle of 28 ° <2θ <29 °, and a diffraction angle of 30.5 ° <2θ <31.5 ° Within the range, a peak attributed to the MgSiO 3 crystal may appear.
본 발명에 의한 음극활물질은 Mg 2SiO 4(forsterite)결정을 더 포함할 수 있다.The negative electrode active material according to the present invention may further include a Mg 2 SiO 4 (forsterite) crystal.
본 발명에 의한 음극활물질은 상기 규소복합산화물 전체 100 중량부 당 탄소는 2 내지 20 중량부로 포함될 수 있다.The negative electrode active material according to the present invention contains carbon per 100 parts by weight of the total silicon composite oxide It may be included in 2 to 20 parts by weight.
본 발명에 의한 음극활물질에 있어서, 탄소 피막의 평균 두께는 5 내지 500 nm 일 수 있다.In the negative electrode active material according to the present invention, the average thickness of the carbon film may be 5 to 500 nm.
본 발명에 따른 음극활물질은 X선 회절 패턴 분석에서 규소 결정으로 인한 피크가 나타나고, 회절각 2θ가 28.5 °부근에서 나타나는 피크는 결정 크기가 1 내지 25 nm 인 규소 결정에 의한 것이다. In the anode active material according to the present invention, a peak due to a silicon crystal appears in an X-ray diffraction pattern analysis, and a peak at a diffraction angle of 2θ around 28.5 ° is due to a silicon crystal having a crystal size of 1 to 25 nm.
또한, 본 발명의 탄소-규소복합산화물 복합체에서 마그네슘 도핑량, 즉 복합체 중에 포함되는 마그네슘 함유량, 즉 마그네슘의 비율은 1 내지 15 중량%가 바람직하다. 보다 바람직하게는 4 내지 10 중량% 인 것이 바람직하다.In addition, the doping amount of magnesium in the carbon-silicon composite oxide composite of the present invention, that is, the amount of magnesium contained in the composite, that is, the ratio of magnesium is preferably 1 to 15% by weight. More preferably, it is preferably 4 to 10% by weight.
마그네슘 함유량을 1 중량% 이상으로 하는 것으로, 초기 효율성을 달성할 수 있고 15 중량% 이하로 함으로써, 사이클 특성의 저하 및 취급 안전에 문제가 발생하지 않으므로 적합하다. 즉, 도핑된 마그네슘은 비수 전해질 2차 전지용 음극 재료 중에서 주로 규산 마그네슘으로 존재하고 있는 것이 안정성의 관점에서 바람직하다.When the magnesium content is 1% by weight or more, the initial efficiency can be achieved, and when the content is 15% by weight or less, a decrease in cycle characteristics and a problem in handling safety are not caused, so it is suitable. That is, it is preferable from the viewpoint of stability that the doped magnesium is mainly present as magnesium silicate among the negative electrode materials for nonaqueous electrolyte secondary batteries.
본 발명은 규산 마그네슘을 포함한 점에 특징이 있지만, 규산 마그네슘 결정은 리튬이온과 반응, 즉 합금화가 어렵기 때문에, 본 발명에 따른 음극활물질을 전극으로 한 경우 리튬이온이 급증할 때의 전극의 팽창·수축량을 억제·감소시키기 때문에 바람직하다. 이로 인하여 사이클 특성이 향상될 수 있다.Although the present invention is characterized in that it contains magnesium silicate, magnesium silicate crystals are difficult to react with lithium ions, that is, alloying, so when the negative electrode active material according to the present invention is used as an electrode, the electrode expands when lithium ions rapidly increase. It is preferable because it suppresses and reduces the amount of contraction. This can improve the cycle characteristics.
또한, 본 발명에 의한 이차전지의 음극재용 규소복합산화물은 규산 마그네슘을 함유하여 음극활물질의 비정질화도를 높이고, 음극활물질의 환원 시에 형성될 수 있는 리튬규산염의 성장을 억제하고, 리튬원자의 확산 속도를 향상시키는 효과를 나타낸다. 그리고, 초기 비가역 반응을 억제하여 리튬이차전지의 초기 용량, 수명 특성 및 고율 충/방전 특성 등을 개선할 수 있다.In addition, the silicon composite oxide for a negative electrode material of a secondary battery according to the present invention contains magnesium silicate to increase the degree of amorphization of the negative electrode active material, suppress the growth of lithium silicate that may be formed during reduction of the negative electrode active material, and diffusion of lithium atoms. It has the effect of improving the speed. In addition, by suppressing the initial irreversible reaction, the initial capacity, life characteristics, and high rate charging/discharging characteristics of the lithium secondary battery may be improved.
또한, 본 발명에 의한 이차전지의 음극재용 규소복합산화물은 규산 마그네슘을 포함하면서 규소 입자를 둘러싼 연속상으로 형성되므로, 본 발명에 의한 이차전지의 음극재용 규소복합산화물의 매트릭스가 규산 마그네슘에 의해 강도가 강화될 수 있다.In addition, since the silicon composite oxide for a negative electrode material of a secondary battery according to the present invention contains magnesium silicate and is formed in a continuous phase surrounding the silicon particles, the matrix of the silicon composite oxide for the negative electrode material of the secondary battery according to the present invention is strengthened by magnesium silicate. Can be strengthened.
본 발명에서는 예의 검토한 결과, MgSiO 3상 및 Mg 2SiO 4상 비율을 최적화함으로써 초기 효율 및 용량 유지율이 향상되는 것을 발견하였다. 본 발명의 복합체의 제조방법은 산화규소 가스 및 마그네슘 가스를 동일한 용기에서 동시에 발생시켜 그 가스를 증착면에서 냉각하여 회수하는 것을 특징으로 한다. 산화규소와 마그네슘이 균일하게 반응하고 그 결과 원소 농도 분포가 균일한 규소복합산화물의 제조가 가능해진다.In the present invention, as a result of intensive examination, it was found that the initial efficiency and capacity retention rate were improved by optimizing the ratio of the MgSiO 3 phase and the Mg 2 SiO 4 phase. The manufacturing method of the composite according to the present invention is characterized in that silicon oxide gas and magnesium gas are simultaneously generated in the same container, and the gas is cooled on the deposition surface and recovered. Silicon oxide and magnesium react uniformly, and as a result, it becomes possible to produce a silicon composite oxide having a uniform element concentration distribution.
본 발명에 의한 이차전지의 음극재용 규소복합산화물은 규산 마그네슘을 포함하여 폴리이미드를 바인더로 한 전극 페이스트를 제조할 때의 음극재 및 바인더와의 화학 반응이 리튬 도핑의 경우에 비해 억제될 수 있다. 따라서, 이러한 음극재를 이용하여 제작된 전극 페이스트의 안정성이 높아지고, 이에 따라 제조된 음극의 사이클 내구성도 기존에 비해 개선될 수 있으므로 바람직하다.The silicon composite oxide for a negative electrode material of a secondary battery according to the present invention can suppress a chemical reaction with the negative electrode material and the binder when preparing an electrode paste containing polyimide as a binder including magnesium silicate compared to lithium doping. . Therefore, the stability of the electrode paste manufactured by using such a negative electrode material is increased, and the cycle durability of the negative electrode manufactured accordingly can be improved as compared with the conventional one, which is preferable.
또한, 규소복합산화물에 대한 탄소 코팅량(탄소 함량)은 2 내지 15 중량% 인 것이 바람직하다. 마그네슘이 도핑되고 한편 탄소 피막이 2 내지 15 중량% 범위로 피복된 탄소-규소복합산화물 복합체에 함유된 규소는 결정자는 크기가 3 내지 20 nm의 결정 상태에서 산화규소계 활물질에 분산된 구조를 갖는 것이 바람직하다.In addition, the amount of carbon coating (carbon content) for the silicon composite oxide is preferably 2 to 15% by weight. Silicon contained in the carbon-silicon composite oxide composite doped with magnesium and coated with a carbon film in the range of 2 to 15% by weight has a structure in which the crystallites are dispersed in a silicon oxide-based active material in a crystal state of 3 to 20 nm in size. desirable.
본 발명에 따른 음극활물질, 즉 탄소-규소복합산화물 복합체에 있어서 탄소 코팅의 평균 두께는 5 내지 500 nm 일 수 있다. 더 바람직하게는 5 내지 200 nm 일 수 있다.In the negative electrode active material according to the present invention, that is, the carbon-silicon composite oxide composite, the average thickness of the carbon coating may be 5 to 500 nm. More preferably, it may be 5 to 200 nm.
규소 표면을 탄소 피복하여 도전화하고 비정질 금속층으로 피복하는 음극재의 사이클 특성을 향상하는 방법으로는 규소 본래의 배터리 용량의 절반 정도를 발휘하는 것에 불과하여 고용량화가 요구되고 있었다. 또한, 결정 입계를 갖는 다결정 규소는 공개된 방법으로는 냉각 속도의 제어가 곤란하고, 안정된 물성을 재현하는 것이 어려웠다.As a method of improving the cycle characteristics of a negative electrode material that is conductive by carbon coating on the silicon surface and coated with an amorphous metal layer, a high capacity has been demanded because it exhibits only about half of the original battery capacity of silicon. Further, for polycrystalline silicon having grain boundaries, it is difficult to control the cooling rate by the disclosed method, and it is difficult to reproduce stable physical properties.
또한, 전기 전도성을 향상시키기 위해 규소복합산화물의 표면이 탄소 피막이 균일하게 형성되어 있다. 탄소 피막이 형성됨으로써 활물질의 초기 효율 및 수명 특성을 향상할 수 있다.In addition, in order to improve electrical conductivity, a carbon film is uniformly formed on the surface of the silicon composite oxide. By forming the carbon film, the initial efficiency and lifespan characteristics of the active material can be improved.
규소산화물복합체 전체 100 중량부당 탄소는 2 내지 15 중량%의 비율로 포함되는 것이 바람직하다. 보다 바람직하게는 3 내지 10 중량%이다.It is preferable that carbon is contained in an amount of 2 to 15% by weight per 100 parts by weight of the total silicon oxide complex. It is more preferably 3 to 10% by weight.
탄소 함량이 2 중량% 미만에서는 충분한 도전성 향상 효과를 기대할 수 없으며, 리튬 이차 전지의 전극 수명이 저하 될 우려가 있다. 탄소 함량이 15 중량%를 초과하면 방전 용량이 감소하고 높은 에너지를 얻기 어렵기 때문에 바람직하지 않다. 또한, 부피 밀도가 작아져, 단위 부피당의 충/방전 용량이 저하되는 경우가 있다.If the carbon content is less than 2% by weight, a sufficient effect of improving conductivity cannot be expected, and there is a concern that the electrode life of the lithium secondary battery may be reduced. If the carbon content exceeds 15% by weight, it is not preferable because the discharge capacity decreases and it is difficult to obtain high energy. Moreover, the bulk density becomes small, and the charge/discharge capacity per unit volume may decrease.
본 발명에 의한 음극활물질에 있어서, 탄소 피막은 탄소 나노 섬유, 그래핀, 산화 그래핀 및 환원된 산화 그래핀으로 이루어진 그룹에서 선택되는 어느 하나 이상을 포함할 수 있다.In the negative electrode active material according to the present invention, the carbon film may include any one or more selected from the group consisting of carbon nanofibers, graphene, graphene oxide, and reduced graphene oxide.
본 발명에 의한 음극활물질에 있어서, 탄소를 피복한 규소 복합 산화물의 비중은 1.8 내지 3.2 일 수 있다. 탄소를 피복한 규소복합산화물, 즉 탄소-규소복합산화물 복합체의 비중은 1.8 내지 2.6 인 것이 바람직하다. 보다 바람직하게는 2.0 내지 2.5 이다. 본 발명에 의한 음극활물질에 있어서, 탄소 코팅양에 따라 비중은 다르다. 탄소량을 고정했을 때 비중이 크면 입자 내부의 기공이 줄어들기 때문에 음극 재료로 사용한 경우, 전도성의 향상뿐만 아니라, 매트릭스의 강도가 강화되고, 초기 효율 또는 사이클 수명 특성을 향상시킬 수 있다. In the negative electrode active material according to the present invention, the specific gravity of the silicon composite oxide coated with carbon may be 1.8 to 3.2. The specific gravity of the silicon composite oxide coated with carbon, that is, the carbon-silicon composite oxide composite is preferably 1.8 to 2.6. More preferably, it is 2.0 to 2.5. In the negative electrode active material according to the present invention, the specific gravity is different depending on the amount of carbon coating. When the amount of carbon is fixed, the pores inside the particles decrease when the specific gravity is large, so when used as a negative electrode material, not only the conductivity is improved, but also the strength of the matrix is strengthened, and the initial efficiency or cycle life characteristics can be improved.
비중이 1.8 내지 2.6 인 범위에 있으면, 900 내지 3000 mAh/g의 높은 배터리 용량을 나타내는 것과 동시에, 쿨롱 효율이 높아진다. 체적 팽창이 적은 흑연계 재료와의 혼합 사용에 있어서도 규소 입자만 크고 부피 팽창을 일으키지 않기 때문에 흑연 재료와 규소 입자의 분리가 작고 사이클 특성이 뛰어난 비수전해질 이차전지를 얻을 수 있다.When the specific gravity is in the range of 1.8 to 2.6, it exhibits a high battery capacity of 900 to 3000 mAh/g and increases the coulomb efficiency. Even when mixed with a graphite-based material having low volume expansion, only the silicon particles are large and do not cause volume expansion, so that the separation of the graphite material and the silicon particles is small, and a nonaqueous electrolyte secondary battery having excellent cycle characteristics can be obtained.
또한, 비중을 1.8 이상으로 함으로써 충전 시 음극활물질 분말의 부피 팽창에 의한 음극활물질 분말끼리의 괴리가 막히고 사이클 열화가 억제된다. 비중을 2.6 이하로 함으로써 전해액의 함침성이 향상되고 음극활물질의 이용률이 높아 초기 충/방전 용량이 향상된다.In addition, when the specific gravity is set to 1.8 or more, separation between the negative electrode active material powders due to volume expansion of the negative electrode active material powder during charging is blocked and cycle deterioration is suppressed. By setting the specific gravity to 2.6 or less, the impregnation property of the electrolyte solution is improved and the utilization rate of the negative electrode active material is increased, thereby improving the initial charge/discharge capacity.
또한, 비중이 상기 범위에 있으면, 본 복합체와 리튬의 반응 속도가 원하는 범위 내이며, 본 복합체 중의 규소 입자에 리튬의 삽입이 제대로 수행되어 사이클 특성이 더 향상된다.In addition, when the specific gravity is in the above range, the reaction rate of the composite and lithium is within the desired range, and the insertion of lithium into the silicon particles in the composite is properly performed, thereby further improving the cycle characteristics.
본 발명에서는 비중은 진비중과 진밀도는 같은 의미로 표현된다. 또한, 건식 비중계에 의한 비중 측정 조건은 예를 들면 다음과 같다. In the present invention, the specific gravity and the true density are expressed in the same meaning. In addition, the specific gravity measurement conditions by a dry hydrometer are as follows, for example.
건식 밀도 측정기로는 주식회사 마이크로매트릭스사의 아큐핏 II 1340을 사용할 수 있다. 사용하는 가스는 헬륨이고, 23 ℃로 설정한 샘플 홀더 내에서 측정한다.As a dry density meter, Micromatrix Inc.'s Accupit II 1340 can be used. The gas used is helium, and it is measured in a sample holder set at 23°C.
또한, 결정자 지름이 20 nm 이하의 규소 입자 및 상술한 비중을 갖는 본 복합체를 비수전해질 이차전지의 음극재료(음극 활물질)에 사용하면 활성 물질의 단위 무게 당 전지 용량은 1500 내지 3000 mAh/g이 되고, 규소 활물질의 단위 중량 당 이론 배터리 용량(4200 mAh/g)에 비해 감소하지만, 높은 전자 전도성과 동시에 부피 팽창이 비교적 작고 사이클 특성이 높은 비수 전해질 이차 전지의 음극을 제공 할 수 있고, 탄소계 음극활물질과 혼합하여 사용하는 경우에도 쿨롱 효율이 높고, 양호한 사이클 특성을 얻을 수 있기 때문에 바람직하다.In addition, when silicon particles having a crystallite diameter of 20 nm or less and this composite having the above-described specific gravity are used for a negative electrode material (cathode active material) of a nonaqueous electrolyte secondary battery, the battery capacity per unit weight of the active material is 1500 to 3000 mAh/g. It is reduced compared to the theoretical battery capacity (4200 mAh/g) per unit weight of the silicon active material, but it can provide a negative electrode of a nonaqueous electrolyte secondary battery with high electronic conductivity and relatively small volume expansion and high cycle characteristics. Even when used in combination with a negative electrode active material, it is preferable because the coulomb efficiency is high and good cycle characteristics can be obtained.
본 발명에 의한 음극활물질에 있어서, 탄소를 피복한 규소 복합 산화물의 평균 입경은 0.1 내지 15 μm 일 수 있다. 탄소를 피복한 탄소-규소복합산화물 복합체는 레이저 회절법에 의해 측정한 부피 기준 분포에서 누적 50 % 크기 D 50인 평균 입자 직경은 2.0 내지 10 μm가 바람직하다. 보다 바람직하게는 2 내지 8 μm이다. 본 발명에 의한 음극활물질에 있어서, 평균 입자 크기가 너무 작으면 부피 밀도가 2.0 μm 이하에서는 단위 부피당의 충/방전 용량이 감소하고, 반대로 평균 입자 지름이 10 μm를 초과하면 전극막 제작이 어렵고 집전체에서 떨어질 우려가 있다. 또한, 평균 입자 지름은 레이저 회절법에 의한 입도 분포 측정에 있어서의 누적 부피 평균 D 50(즉, 누적 부피 평균이 50%가 될 때의 입자 지름 또는 메디안 직경)으로 측정한 값이다.In the negative electrode active material according to the present invention, the average particle diameter of the silicon composite oxide coated with carbon may be 0.1 to 15 μm. The carbon-silicon composite oxide composite coated with carbon preferably has an average particle diameter of 2.0 to 10 μm with a cumulative 50% size D 50 in a volume-based distribution measured by a laser diffraction method. More preferably, it is 2 to 8 μm. In the negative electrode active material according to the present invention, when the average particle size is too small, the charge/discharge capacity per unit volume decreases when the bulk density is 2.0 μm or less, and conversely, when the average particle diameter exceeds 10 μm, it is difficult to manufacture an electrode film. There is a risk of falling from the whole. In addition, the average particle diameter is a value measured by the cumulative volume average D 50 (that is, the particle diameter or median diameter when the cumulative volume average becomes 50%) in the particle size distribution measurement by laser diffraction method.
분쇄 후 입도 분포를 얻기 위해 건식 분급 및 습식 분급 혹은 체로 분급할 수 있다. 건식 분급은 주로 기류를 이용하고, 분산, 분리(미세 입자와 굵은 입자의 분리), 포집(고체와 기체의 분리), 배출의 과정이 순차적으로 또는 동시에 이루어 지고, 입자 상호간의 간섭, 입자 모양, 기류의 흐름의 혼란, 속도 분포, 정전기의 영향 등으로 분급 효율을 저하시키지 않도록 분급을 하기 전에 전처리(수분, 분 산성, 습도 등의 조정)를 실시한다. 또한, 사용되는 기류의 수분이나 산소 농도를 조절하여 사용된다. 또한, 사이클론 등의 건식 분급기가 일체되어 있는 타입은 한번에 분쇄, 분급이 이루어져 원하는 입도 분포를 얻는 것이 가능해진다. 분쇄 후 분급기나 체로 조분측 및 과립측을 제거하는 것이 효과적이다.After pulverization, it can be classified by dry classification, wet classification or sieve to obtain particle size distribution. Dry classification mainly uses airflow, and the processes of dispersion, separation (separation of fine particles and coarse particles), collection (separation of solid and gas), and discharge are performed sequentially or simultaneously, and interference between particles, particle shape, Pre-treatment (adjustment of moisture, dispersibility, humidity, etc.) is carried out before classification so as not to reduce classification efficiency due to confusion of airflow, velocity distribution, and the influence of static electricity. Also, it is used by controlling the moisture or oxygen concentration of the used air stream. In addition, a type in which a dry classifier such as a cyclone is integrated can be pulverized and classified at once to obtain a desired particle size distribution. It is effective to remove the coarse and granular side with a classifier or sieve after grinding.
위의 분급 처리하여 평균 입자 직경이 2 내지 8 μm의 분말을 이용하면 초기 효율과 사이클 특성이 분급 전에 비해 10 내지 20% 향상될 수 있다. 분급 후 분말의 최대입경(Dmax)가 20 μm 이하이면 바람직하다. 이 범위의 본 복합체 분말의 비표면적이 감소한다. 그 결과, SEI(Solid Electrolyte Interface)에 추가되는 리튬이 감소할 수 있다.If powder having an average particle diameter of 2 to 8 μm is used by the above classification treatment, initial efficiency and cycle characteristics can be improved by 10 to 20% compared to before classification. It is preferable that the maximum particle diameter (Dmax) of the powder after classification is 20 μm or less. The specific surface area of this composite powder in this range is reduced. As a result, lithium added to the SEI (Solid Electrolyte Interface) may be reduced.
또한, 분급 처리 후 분말은 비정질 입계 및 결정질 입계를 가지고 있으며, 비정질 입계 및 결정질 입계의 응력 완화 효과에 의해 충/방전 사이클에서의 입자 붕괴가 억제된다. 따라서, 이러한 분말을 비수전해질 이차전지의 음극재에 이용하는 것으로, 비수 전해질 이차 전지의 음극 재료가 충/방전에 의한 체적 팽창 변화의 응력에 견딜 수 있기 때문에 이러한 분말을 이용한 비수전해질 이차전지는 바람직하고, 본 발명에 의한 음극활물질에 있어서 탄소를 피복한 규소복합산화물의 비표면적은 1 내지 40 m 2/g 일 수 있다.In addition, the powder after classification treatment has an amorphous grain boundary and a crystalline grain boundary, and particle collapse in a charge/discharge cycle is suppressed by the stress relaxation effect of the amorphous grain boundary and the crystalline grain boundary. Therefore, by using such powder as a negative electrode material of a nonaqueous electrolyte secondary battery, a nonaqueous electrolyte secondary battery using such powder is preferable because the negative electrode material of the nonaqueous electrolyte secondary battery can withstand the stress of volume expansion change due to charge/discharge. , In the negative electrode active material according to the present invention, the specific surface area of the silicon composite oxide coated with carbon may be 1 to 40 m 2 /g.
탄소를 피복한 복합체의 비표면적은 3 내지 20 m 2/g 인 것이 바람직하다. 또한, 상기 복합체의 비표면적이 3 m 2/g 미만인 경우 레이트 특성이 저하되어 바람직하지 않다. 상기 복합체의 비표면적이 20 m 2/g을 초과하는 경우, 전해액과의 접촉 면적이 증가하여 전해액의 분해 반응이 촉진될 우려가 있으며, 전지 부반응을 일으켜 바람직하지 않다. 보다 바람직하게는 4 내지 10 m 2/g 이다. The specific surface area of the composite coated with carbon is preferably 3 to 20 m 2 /g. In addition, when the specific surface area of the composite is less than 3 m 2 /g, rate characteristics are deteriorated, which is not preferable. When the specific surface area of the composite exceeds 20 m 2 /g, the contact area with the electrolyte may increase, thereby accelerating the decomposition reaction of the electrolyte, which is undesirable because a side reaction of the battery may occur. More preferably, it is 4 to 10 m 2 /g.
본 발명에 따른 음극활물질은 전체 음극활물질 100 중량부에 대하여 탄소-규소복합산화물 복합체가 5 내지 70 중량부로 포함될 수 있다.The negative electrode active material according to the present invention contains a carbon-silicon composite oxide composite based on 100 parts by weight of the It may be included in 5 to 70 parts by weight.
본 발명에 의한 리튬이차전지용 음극활물질은 탄소-규소복합산화물 복합체와 탄소계 물질을 혼합시킴으로써, 음극활물질층의 전기 저항을 저감함과 동시에 충전에 따른 팽창 응력을 완화하는 것이 가능해진다. 이 탄소계 물질은, 예를 들면, 열분해 탄소류, 코크스류, 탄소 섬유, 유기 고분자 화합물 소성체, 카본 블랙류 등이 있다. 본 발명에 따른 음극활물질은 탄소-규소복합산화물 복합체와 탄소계 물질의 혼합물의 탄소계 음극활물질의 함유량이 30 내지 95 중량% 인 것이 가능하며, 바람직하게는 50 내지 90 중량% 이면 좋다.The negative electrode active material for a lithium secondary battery according to the present invention may reduce the electrical resistance of the negative electrode active material layer and at the same time alleviate the expansion stress caused by charging by mixing the carbon-silicon composite oxide composite and the carbon-based material. Examples of the carbon-based material include pyrolytic carbons, coke, carbon fibers, fired organic polymer compounds, and carbon blacks. In the negative electrode active material according to the present invention, the content of the carbon-based negative electrode active material in the mixture of the carbon-silicon composite oxide composite and the carbon-based material may be 30 to 95% by weight, preferably 50 to 90% by weight.
또한, 본 발명의 탄소-규소복합산화물 복합체를 포함하는 리튬이차전지는 고용량이고 긴수명의 배터리 특성을 나타낸다.In addition, the lithium secondary battery including the carbon-silicon composite oxide composite of the present invention exhibits high capacity and long life battery characteristics.
본 발명은 또한, The present invention also,
분말을 혼합하여 Si / SiO 2 원료분말혼합체를 제조하는 제 1 단계; A first step of mixing the powder to prepare a Si / SiO 2 raw material powder mixture;
상기 Si / SiO 2 원료분말혼합체와 금속 마그네슘을 동시 또는 순차적으로 증발 및 증착시켜 규소복합산화물을 형성하는 제 2 단계; A second step of simultaneously or sequentially evaporating and depositing the Si / SiO 2 raw material powder mixture and metal magnesium to form a silicon composite oxide;
상기 제 2 단계에서 제조된 규소복합산화물을 냉각시키는 제 3 단계; A third step of cooling the silicon composite oxide prepared in the second step;
상기 제 3 단계에서 제조된 규소복합산화물을 분쇄/분급하는 제 4 단계; A fourth step of grinding/classifying the silicon composite oxide prepared in the third step;
상기 제 4 단계에서 제조된 규소복합산화물의 표면을 탄소로 피복시키는 제 5 단계를 포함하는 리튬이차전지용 음극활물질의 제조방법을 제공한다.It provides a method for producing a negative electrode active material for a lithium secondary battery comprising a fifth step of covering the surface of the silicon composite oxide prepared in the fourth step with carbon.
본 발명에 의한 리튬이차전지용 음극활물질의 제조방법에 있어서, 상기 제 1 단계에 Si / SiO 2 원료분말혼합체는 규소 1 몰 당 이산화규소를 0.2 내지 1.5 몰의 비율로 혼합하는 것을 특징으로 한다.In the method for producing a negative electrode active material for a lithium secondary battery according to the present invention, the Si / SiO 2 raw material powder mixture in the first step is characterized in that silicon dioxide is mixed in a ratio of 0.2 to 1.5 moles per mole of silicon.
본 발명에 의한 리튬이차전지용 음극활물질의 제조방법에 있어서, 상기 제 1 단계에 사용 규소 분말 및 이산화규소 분말은 각각 평균 입경이 10 nm 내지 0.5μｍ 및 10 nm 내지 100 nm 일 수 있다.In the method of manufacturing a negative electrode active material for a lithium secondary battery according to the present invention, the silicon powder and the silicon dioxide powder used in the first step may have an average particle diameter of 10 nm to 0.5 μm and 10 nm to 100 nm, respectively.
본 발명에 의한 리튬이차전지용 음극활물질의 제조방법에 있어서, 상기 제 1 단계에서 Si는 산소를 포함할 수 있고, Si/SiO 2 원료분말혼합체는 규소 1 몰 당 이산화 규소를 0.2 내지 1.5 몰의 비율로 혼합할 수 있다. 더욱 바람직하게는 0.8 내지 1.2 몰의 비율로 혼합할 수 있다. 본 발명에 따른 리튬이차전지용 음극활물질의 제조방법에 있어서는, 제 1 단계에서 사용되는 규소 분말과 이산화규소 분말은 각각 50 nm 내지 50 μm과 10 내지 100 nm의 평균 입자 크기를 나타내는 것이 바람직하다. In the method for producing a negative electrode active material for a lithium secondary battery according to the present invention, in the first step, Si may contain oxygen, and the Si/SiO 2 raw material powder mixture contains 0.2 to 1.5 moles of silicon dioxide per mole of silicon. Can be mixed with. More preferably, it can be mixed in a ratio of 0.8 to 1.2 mol. In the method for producing a negative electrode active material for a lithium secondary battery according to the present invention, it is preferable that the silicon powder and the silicon dioxide powder used in the first step have an average particle size of 50 nm to 50 μm and 10 to 100 nm, respectively.
본 발명에 의한 리튬이차전지용 음극활물질의 제조방법에 있어서, 상기 제 1 단계에서 Si는 산소를 포함할 수 있고, Si/SiO 2 원료분말혼합체는 산소/규소 원자 비율이 1 내지 1.5 인 것이 바람직하며, 더욱 바람직하게는 산소/규소 원자 비율이 1 내지 1.1 이다.In the method for producing a negative electrode active material for a lithium secondary battery according to the present invention, in the first step, Si may contain oxygen, and the Si/SiO 2 raw material powder mixture preferably has an oxygen/silicon atom ratio of 1 to 1.5. , More preferably, the oxygen/silicon atom ratio is 1 to 1.1.
본 발명에서는 Si / SiO 2 원료분말혼합체 대신에 SiOx(0.9 < x < 1.5)를 사용할 수 있으며 SiO가 바람직할 수 있다.In the present invention, SiOx (0.9 <x <1.5) may be used instead of the Si / SiO 2 raw material powder mixture, and SiO may be preferred.
본 발명에 의한 리튬이차전지용 음극활물질의 제조방법에 있어서, 상기 제2 단계의 증발은 0.00001 내지 2 torr의 압력하에서 600 내지 1600 ℃로 가열하여 수행될 수 있다.In the method of manufacturing a negative active material for a lithium secondary battery according to the present invention, the evaporation in the second step may be performed by heating at 600 to 1600° C. under a pressure of 0.00001 to 2 torr.
본 발명에 의한 리튬이차전지용 음극활물질의 제조방법에 있어서, 상기 제 3 단계의 냉각 과정은 수냉 기판에 의한 냉각, 자연 냉각 및 기타 냉각 방법 중 어느 하나의 방법에 의해 상온까지 냉각될 수 있다.In the method of manufacturing a negative active material for a lithium secondary battery according to the present invention, the cooling process in the third step may be cooled to room temperature by any one of cooling by a water-cooled substrate, natural cooling, and other cooling methods.
본 발명에 의한 리튬이차전지용 음극활물질의 제조방법에 있어서, 상기 제 4 단계의 분쇄 과정은 평균 입경이 ２ 내지 10μｍ가 되도록 분쇄할 수 있다.In the method of manufacturing a negative active material for a lithium secondary battery according to the present invention, the pulverization process in the fourth step may be pulverized so that the average particle diameter is 2 to 10 μm.
본 발명에 의한 리튬이차전지용 음극활물질의 제조방법에 있어서, 상기 5단계의 탄소로 코팅하는 상기 규소복합산화물을 메탄, 에탄, 프로판, 부탄, 에틸렌, 프로필렌, 부타디엔, 메탄올, 에탄올, 프로판올 아세틸렌, 벤젠 및 톨루엔으로부터 선택되는 하나 또는 이들의 조합을 이용하여 600 내지 1200 ℃에서 가스 상태로 반응시키는 것을 특징으로 하며, 아래에서 상세하게 설명한다.In the method for producing a negative electrode active material for a lithium secondary battery according to the present invention, the silicon composite oxide coated with carbon in the 5th step is methane, ethane, propane, butane, ethylene, propylene, butadiene, methanol, ethanol, propanol acetylene, benzene And one selected from toluene or a combination thereof is characterized in that the reaction is performed in a gaseous state at 600 to 1200° C., which will be described in detail below.
본 발명에 의한 이차전지의 음극재용 규소복합산화물에 있어서,　탄소층은 그래핀, 환원된 산화 그래핀 또는/및 탄소 나노 섬유를 주성분으로 형성되는 것이 바람직하며, 아래의 화학식1, 화학식2 및 화학식 3으로 표시되는 탄소원 반응 가스, 반응 시간 및 반응 온도에 의해 변화된다. In the silicon composite oxide for a negative electrode material of a secondary battery according to the present invention, 　 the carbon layer is preferably formed of graphene, reduced graphene oxide or/and carbon nanofibers as a main component, and the following Chemical Formulas 1, 2 and Chemical Formulas It changes with the carbon source reaction gas represented by 3, reaction time, and reaction temperature.
[화학식 1] C nH (2n+2-A)[OH] A [Formula 1] C n H (2n+2-A) [OH] A
상기 화학식 1 중, n은 1 내지 20의 정수, A는 0 또는 1이며,In Formula 1, n is an integer of 1 to 20, A is 0 or 1,
[화학식 2] C nH (2n-A) [Formula 2] C n H (2n-A)
상기 화학식 2 중, n은 2 내지 6의 정수이고, A는 0 또는 1이며In Formula 2, n is an integer of 2 to 6, A is 0 or 1,
[화학식 3] C xH yO z [Chemical Formula 3] C x H y O z
상기 화학식 3 중, x는 0 또는 1 내지 20의 정수이고, y는 0 또는 1 내지 20의 정수이고, z는 0, 1 또는 2이다. In Formula 3, x is 0 or an integer of 1 to 20, y is 0 or an integer of 1 to 20, and z is 0, 1 or 2.
상기 화학식 1로 표시되는 화합물과 화학식 2로 표시되는 화합물은 예를 들면 메탄, 에탄, 프로판, 부탄, 에틸렌, 프로필렌, 부타디엔, 메탄올, 에탄올, 프로판올로 이루어진 군으로부터 선택된 하나 이상이다. 화학식 3으로 표시되는 산소 함유 가스는 예를 들면, 이산화탄소(CO 2)와 일산화탄소(CO), 수증기(H 20), 벤질알코올이며, 화학식 3으로 표시되는 산소를 함유하지 않는 가스는 예를 들면 아세틸렌, 벤젠, 톨루엔, 자일렌 또는 그 혼합물을 포함한다.The compound represented by Formula 1 and the compound represented by Formula 2 are, for example, at least one selected from the group consisting of methane, ethane, propane, butane, ethylene, propylene, butadiene, methanol, ethanol, and propanol. The oxygen-containing gas represented by Formula 3 is, for example, carbon dioxide (CO 2 ), carbon monoxide (CO), water vapor (H 2 O), and benzyl alcohol, and the gas not containing oxygen represented by Formula 3 is, for example, Acetylene, benzene, toluene, xylene or mixtures thereof.
탄소원 가스 이외에 질소, 헬륨, 아르곤 이루어진 군으로부터 선택된 복수의 불활성 가스를 더 포함할 수 있다.In addition to the carbon source gas, a plurality of inert gases selected from the group consisting of nitrogen, helium, and argon may be further included.
상기 산소 함유 가스는 일산화탄소, 이산화탄소, 수증기로 이루어진 군으로부터 선택된 하나 이상일 수 있다.The oxygen-containing gas may be at least one selected from the group consisting of carbon monoxide, carbon dioxide, and water vapor.
본 발명의 실시예에 따른 이차전지 음극재용 규소복합산화물을 갖춘 리튬이차전지용 음극은 상기 제조방법으로 제조된다.A negative electrode for a lithium secondary battery having a silicon composite oxide for a negative electrode material for a secondary battery according to an embodiment of the present invention is manufactured by the above manufacturing method.
본 발명의 실시예에 따른 리튬이차전지는 리튬이차전지용 음극을 구비한다.A lithium secondary battery according to an embodiment of the present invention includes a negative electrode for a lithium secondary battery.
상기 리튬이차전지는 상기 제조방법으로 얻어진 이차전지 음극재용 탄소-규소복합산화물 복합체를 사용하며, 음극으로 흑연을 더 포함하는 것이 가능하다.The lithium secondary battery uses a carbon-silicon composite oxide composite for a secondary battery negative electrode material obtained by the above manufacturing method, and may further include graphite as a negative electrode.
본 발명에 의한 탄소-규소복합산화물 복합체는 충/방전 용량을 향상시키고, 초기 충/방전 효율을 높이며 용량 유지율도 향상된 비수전해질 리튬이차전지를 제조할 수 있다. The carbon-silicon composite oxide composite according to the present invention improves charge/discharge capacity, improves initial charge/discharge efficiency, and improves capacity retention.
본 발명에서는, Si/SiO 2 원료분말혼합체와 마그네슘을 함께 가열시켜 증발된 입자들의 균일한 기상반응으로 규소복합산화물이 합성되며, 고상반응에서와 같이 Mg이 국부적으로 과잉 혼합되면서 일어나는 발열 반응에 의해 규소가 급격히 성장하는 것을 방지하여 용량 유지율을 향상시키는 것이 가능하다. In the present invention, the silicon composite oxide is synthesized by a uniform gas phase reaction of the evaporated particles by heating the Si/SiO 2 raw material powder mixture and magnesium together, and the exothermic reaction that occurs when Mg is locally excessively mixed as in the solid phase reaction. It is possible to improve the capacity retention rate by preventing the silicon from growing rapidly.
또한, 본 발명에 의한 규소복합산화물의 제조방법은 Mg 2SiO 4(forsterite)의 생성보다는 MgSiO 3(enstatite)가 주로 생성되게 하여, 적은 양의 Mg으로 규소복합산화물의 비가역 물질인 Mg 2SiO 4(forsterite), MgSiO 3(enstatite)를 효율적으로 제어하여 단위 무게당 용량을 향상시키는 것이 가능하다.In addition, the manufacturing method of the silicon composite oxide according to the present invention mainly produces MgSiO 3 (enstatite) rather than the formation of Mg 2 SiO 4 (forsterite), so that Mg 2 SiO 4 is an irreversible material of the silicon composite oxide with a small amount of Mg. It is possible to improve the capacity per unit weight by efficiently controlling (forsterite) and MgSiO 3 (enstatite).
도 1은 본 발명의 실시예 1에 의해 제조된 탄소-규소복합산화물 복합체의 표면을 투과전자현미경(TEM)을 이용하여 분석한 결과를 나타낸다. 1 shows the results of analyzing the surface of the carbon-silicon composite oxide composite prepared in Example 1 of the present invention using a transmission electron microscope (TEM).
도 2 내지 도 6은 본 발명의 실시예 및 비교예에서 의해 제조된 규소복합산화물의 X선 회절분석 결과 그래프이다. 2 to 6 are graphs of the results of X-ray diffraction analysis of silicon composite oxides prepared in Examples and Comparative Examples of the present invention.
이하, 실시예를 통하여 본 발명을 더욱 상세히 설명하기로 한다. 이들 실시예는 단지 본 발명을 예시하기 위한 것이므로, 본 발명의 범위가 이들 실시예에 의해 제한되는 것으로 해석되지는 않는다.Hereinafter, the present invention will be described in more detail through examples. Since these examples are for illustrative purposes only, the scope of the present invention is not to be construed as being limited by these examples.
<실시예 1> 탄소-규소복합산화물 복합체 제조<Example 1> Preparation of carbon-silicon composite oxide composite
(1) 제 1 단계: 평균입자크기가 20 ㎛인 규소분말 8 kg과 평균입자크기가 20 nm인 이산화규소분말 16 kg을 물 50 kg에 넣고 2시간 교반하여 균일하게 혼합 후에, 150 ℃에서 2 시간 건조하여 원료분말혼합체를 형성하였다.(1) Step 1: Add 8 kg of silicon powder with an average particle size of 20 µm and 16 kg of silicon dioxide powder with an average particle size of 20 nm in 50 kg of water, stir for 2 hours to uniformly mix, and then at 150°C. Drying for an hour to form a raw material powder mixture.
(2) 제 2 단계: 상기 원료분말혼합체와 금속마그네슘 0.6 kg을 각각 진공반응기의 도가니-A와 도가니-B에 투입하고, 감압시켜 0.1 torr에 도달된 후, 가열하여 도가니-A는 1500 ℃까지 도가니-B는 900 ℃까지 승온시키고 5 시간 동안 반응시켰다.(2) Step 2: Put the raw material powder mixture and 0.6 kg of metal magnesium into crucibles-A and crucible-B of a vacuum reactor, respectively, to reach 0.1 torr by decompressing, and heating to crucible-A to 1500°C The crucible-B was heated to 900° C. and reacted for 5 hours.
(3) 제 3 단계: 상기 고온의 기상에서 반응시켜 반응기 내부의 기판에 증착된 규소복합산화물 덩어리를 수냉 기판에 의해 실온까지 빠르게 냉각시켰다.(3) Third step: The silicon composite oxide mass deposited on the substrate inside the reactor by reacting in the high temperature gas phase was rapidly cooled to room temperature by a water-cooled substrate.
(4) 제 4 단계: 상기 규소복합산화물 덩어리를 입도 제어를 위하여 기계적인 방법으로 분쇄하여 평균입경이 6 ㎛가 되도록 하였다.(4) Fourth step: The silicon composite oxide mass was pulverized by a mechanical method to control the particle size so that the average particle diameter was 6 µm.
(5) 제 5 단계: 상기 분쇄된 규소복합산화물 분말 50 g을 튜브형 전기로 내부에 넣고 알곤과 메탄가스를 각각 1 L/min씩 흘려주면서 900 ℃에서 1 시간 동안 유지하여 표면이 탄소로 피복된 탄소-규소복합산화물 복합체 분말을 제조하였다. (5) Step 5: Put 50 g of the pulverized silicon composite oxide powder inside a tube-type electric furnace, and keep argon and methane gas at 900° C. for 1 hour while flowing 1 L/min each, so that the surface is covered with carbon. A carbon-silicon composite oxide composite powder was prepared.
<실험예 1> 투과전자현미경(TEM) 분석<Experimental Example 1> Transmission electron microscope (TEM) analysis
상기 제조된 탄소-규소복합산화물 복합체의 표면을 투과전자현미경(TEM)을 이용하여 분석하고 그 결과를 도 1에 나타내었다.The surface of the prepared carbon-silicon composite oxide composite was analyzed using a transmission electron microscope (TEM), and the results are shown in FIG. 1.
<실험예2> 성분 원소의 함량 및 비중 분석<Experimental Example 2> Analysis of the content and specific gravity of component elements
상기 제조된 탄소-규소복합산화물 복합체 중 마그네슘(Mg), 산소(O) 및 탄소(C)의 각 성분 원소의 함량을 분석하였다. The content of each component element of magnesium (Mg), oxygen (O), and carbon (C) in the prepared carbon-silicon composite oxide composite was analyzed.
마그네슘(Mg) 함량은 유도결합 플라즈마(ICP) 발광 분광법에 의해 분석되었으며, 산소(O) 및 탄소(C) 함량은 원소분석기(Elemental Analyzer)에 의해 각각 분석되었다. The content of magnesium (Mg) was analyzed by inductively coupled plasma (ICP) emission spectroscopy, and the content of oxygen (O) and carbon (C) was analyzed by an elemental analyzer, respectively.
상기 실시예 1에서 제조된 탄소-규소복합산화물 복합체의 마그네슘 함량은 2.3 wt%이며, 원소분석기에 의하여 분석된 산소 함량은 34.1 wt%, 탄소 함량은 5 wt% 이였다. The magnesium content of the carbon-silicon composite oxide composite prepared in Example 1 was 2.3 wt%, the oxygen content analyzed by the elemental analyzer was 34.1 wt%, and the carbon content was 5 wt%.
분석된 규소복합산화물의 각 성분 원소의 함량을 아래 표 1에 나타내었다.The content of each component element of the analyzed silicon composite oxide is shown in Table 1 below.
실시예1Example 1 실시예2Example 2 실시예3Example 3 실시예4Example 4 실시예5Example 5 비교예1Comparative Example 1 비교예2Comparative Example 2 비교예3Comparative Example 3
Mg At%Mg At% 2.132.13 5.765.76 11.1211.12 11.9211.92 5.555.55 -- 1.791.79 22.6322.63
Si At%Si At% 50.4950.49 48.5548.55 44.6644.66 42.1342.13 48.0848.08 50.3950.39 44.9144.91 48.3648.36
O At%O At% 47.3847.38 45.6945.69 44.2244.22 45.9545.95 46.3746.37 49.6149.61 53.3053.30 2929
O/(Mg+Si)O/(Mg+Si) 0.900.90 0.840.84 0.790.79 0.850.85 0.860.86 0.980.98 1.141.14 0.410.41
Si/MgSi/Mg 23.723.7 8.438.43 4.024.02 3.533.53 8.678.67 00 25.0925.09 2.132.13
<실험예 3> 입자 평균입경 측정<Experimental Example 3> Measurement of particle average particle diameter
상기 제조된 분말의 평균입경(입자직경)은, 레이저 광 회절법에 의한 입도 분포 측정에 있어서의 부피 평균치 D 50(누적 부피가 전 부피의 50%가 될 때의 입자 직경 또는 메디안 직경)으로 측정되었다.The average particle diameter (particle diameter) of the prepared powder is measured by the volume average value D 50 (particle diameter or median diameter when the cumulative volume becomes 50% of the total volume) in the particle size distribution measurement by laser light diffraction method. Became.
BET는 6.7 m 2/g이며, 비중은 2.3, D 50은 6 μm, XRD의 시라법에 의한 규소결정크기는 9.5 nm로 측정되었다.The BET was 6.7 m 2 /g, the specific gravity was 2.3, the D 50 was 6 μm, and the silicon crystal size by XRD was 9.5 nm.
<실험예4> X선 회절패턴 분석<Experimental Example 4> X-ray diffraction pattern analysis
상기 실시예 1에서 제조된 탄소-규소복합산화물 복합체의 결정구조를 X선 회절패턴을 이용하여 분석하였다.The crystal structure of the carbon-silicon composite oxide composite prepared in Example 1 was analyzed using an X-ray diffraction pattern.
X선 회절패턴에서 보이는 것처럼, 본 발명에서 제조된 탄소-규소복합산화물 복합체는 회절각(2θ) 28.5 °부근에서 Si 결정에 귀속되는 피크와 회절각(2θ) 31.0 °부근에서 MgSiO 3 결정에 귀속되는 피크가 나타나 결정질 Si과 MgSiO 3로 이루어지는 것을 알 수 있었다. As shown in the X-ray diffraction pattern, the carbon-silicon composite oxide composite prepared in the present invention belongs to the Si crystal at a diffraction angle (2θ) of 28.5 ° and a peak attributable to the diffraction angle (2θ) 31.0 ° to the MgSiO 3 crystal. It was found that the peak appeared and was composed of crystalline Si and MgSiO 3 .
각 원소 성분의 함량으로부터 비정질산화규소(SiOx)와 탄소도 함유되어 있는것을 알 수 있었다. From the content of each elemental component, it was found that amorphous silicon oxide (SiOx) and carbon were also contained.
얻어진 탄소-규소복합산화물 복합체 중의 Si 결정크기(crystal size)는 X선회절패턴에서 Si(111)에 귀속되는 피크의 반가치폭(FWHM, Full Width at Half Maximum)을 기초로 아래 일반식(1)로 표현되는 시라법(sherrer equation)에 의해 분석되었다.The Si crystal size in the obtained carbon-silicon composite oxide composite is based on the following general formula (1) based on the full width at half maximum (FWHM) of the peak attributable to Si(111) in the X-ray diffraction pattern. It was analyzed by the Sherrer equation expressed as.
C.S.[㎚] = Kλ/ Bcosθ - 일반식 (1)C.S.[nm] = Kλ/ Bcosθ-General formula (1)
(상기 일반식 (1)에서, K= 0.9, λ= 0.154 ㎚, B= 반가치폭(FWHM, rad), (In the general formula (1), K = 0.9, λ = 0.154 nm, B = half value width (FWHM, rad),
θ= 피크위치(각도))θ = peak position (angle))
<실시예 2> 탄소-규소복합산화물 복합체 제조<Example 2> Preparation of carbon-silicon composite oxide composite
상기 실시예 1에서 금속마그네슘 2 kg을 넣는 것을 제외하고는, 상기 실시예 1과 동일한 방법으로 탄소-규소복합산화물 복합체 분말을 제조하였다.Except for adding 2 kg of metallic magnesium in Example 1, a carbon-silicon composite oxide composite powder was prepared in the same manner as in Example 1.
상기 표 1에서 보는 바와 같이 상기 제조된 탄소-규소복합산화물 복합체의 마그네슘 함량은 6.2 wt% 이며, 원소분석기에 의하여 분석된 산소 함량은 32.8 wt%, 탄소 함량은 5 wt% 이였다. BET는 5.8 m 2/g 이며, 비중은 2.3, D 50은 6 μm, XRD의 시라법에 의한 규소결정크기는 7.7 nm로 측정되었다.As shown in Table 1, the magnesium content of the prepared carbon-silicon composite oxide composite was 6.2 wt%, the oxygen content analyzed by the elemental analyzer was 32.8 wt%, and the carbon content was 5 wt%. The BET was 5.8 m 2 /g, the specific gravity was 2.3, the D 50 was 6 μm, and the silicon crystal size by XRD was 7.7 nm.
<실시예 3> 탄소-규소복합산화물 복합체 제조<Example 3> Preparation of carbon-silicon composite oxide composite
상기 실시예 1에서 금속마그네슘 4 kg을 넣는 것을 제외하고는, 상기 실시예 1과 동일한 방법으로 탄소-규소복합산화물 복합체 분말을 제조하였다. Except for adding 4 kg of metal magnesium in Example 1, a carbon-silicon composite oxide composite powder was prepared in the same manner as in Example 1.
상기 표 1에서 보는 바와 같이 상기 제조된 탄소-규소복합산화물 복합체의 마그네슘 함량은 12 wt% 이며, 원소분석기에 의하여 분석된 산소 함량은 31.8 wt%, 탄소 함량은 5 wt% 이였다. BET는 6.3 m 2/g 이며, 비중은 2.4, D 50은 6 μm, XRD의 시라법에 의한 규소결정크기는 8.6 nm로 측정되었다.As shown in Table 1, the magnesium content of the prepared carbon-silicon composite oxide composite was 12 wt%, the oxygen content analyzed by the elemental analyzer was 31.8 wt%, and the carbon content was 5 wt%. The BET was 6.3 m 2 /g, the specific gravity was 2.4, the D 50 was 6 μm, and the silicon crystal size by XRD was 8.6 nm.
<실시예 4> 탄소-규소복합산화물 복합체 제조<Example 4> Preparation of carbon-silicon composite oxide composite
상기 실시예 3에서 냉각 온도를 950 ℃로 설정한 것을 제외하고는, 상기 실시예 3과 동일한 방법으로 탄소-규소복합산화물 복합체 분말을 제조하였다. A carbon-silicon composite oxide composite powder was prepared in the same manner as in Example 3, except that the cooling temperature was set to 950°C in Example 3 above.
상기 표 1에서 보는 바와 같이 상기 제조된 탄소-규소복합산화물 복합체의 마그네슘 함량은 13 wt% 이며, 원소분석기에 의하여 분석된 산소 함량은 33.4 wt%, 탄소 함량은 5 wt% 이였다. BET는 6.3 m 2/g 이며, 비중은 2.4, D 50은 6 μm, XRD의 시라법에 의한 규소결정크기는 10.3 nm로 측정되었다.As shown in Table 1, the magnesium content of the prepared carbon-silicon composite oxide composite was 13 wt%, the oxygen content analyzed by the elemental analyzer was 33.4 wt%, and the carbon content was 5 wt%. The BET was 6.3 m 2 /g, the specific gravity was 2.4, the D 50 was 6 μm, and the silicon crystal size by XRD was 10.3 nm.
<실시예 5> 탄소-규소복합산화물 복합체 제조<Example 5> Preparation of carbon-silicon composite oxide composite
상기 실시예 2에서 표면을 탄소로 코팅하기 위해 메탄이 포함된 천연가스로 CVD 처리한 것을 제외하고, 실시예 2와 동일한 방법으로 탄소가 표면에 피복된 탄소-규소복합산화물 복합체 분말을 제조하였다.In Example 2, a carbon-silicon composite oxide composite powder coated with carbon was prepared in the same manner as in Example 2, except that CVD treatment was performed with natural gas containing methane to coat the surface with carbon.
상기 표 1에서 보는 바와 같이 상기 제조된 탄소-규소복합산화물 복합체의 마그네슘 함량은 6 wt% 이며, 원소 분석기에 의하여 분석된 산소 함량은 20.8 wt%, 탄소 함량은 7 wt% 이였다. BET는 6.2 m 2/g 이며, 비중은 2.3, D 50은 6 μm, XRD의 시라법에 의해 규소결정크기는 8.2 nm로 측정되었다.As shown in Table 1, the magnesium content of the prepared carbon-silicon composite oxide composite was 6 wt%, the oxygen content analyzed by the elemental analyzer was 20.8 wt%, and the carbon content was 7 wt%. The BET was 6.2 m 2 /g, the specific gravity was 2.3, the D 50 was 6 μm, and the silicon crystal size was measured to be 8.2 nm by the Sira method of XRD.
<비교예 1> 탄소-규소산화물 복합체의 제조 <Comparative Example 1> Preparation of carbon-silicon oxide composite
상기 실시예 1의 제2 단계에서 금속마그네슘 2 kg을 도가니-B에 투입하는 것과 도가니-B를 900 ℃까지 가열하는 것을 제외하고, 상기 실시예 1과 동일한 방법으로 탄소가 표면에 피복된 탄소-규소산화물 복합체를 제조하였다.In the second step of Example 1, except that 2 kg of metal magnesium was added to the crucible-B and the crucible-B was heated to 900° C., carbon coated on the surface of the carbon-coated surface in the same manner as in Example 1- A silicon oxide composite was prepared.
상기 표 1에서 보는 바와 같이 상기 제조된 탄소-규소산화물 복합체의 원소분석기에 의하여 분석된 산소 함량은 36 wt%, 탄소 함량은 5 wt% 이였다. BET는 6.3 m 2/g 이며, 비중은 2.2, D 50은 6 μm, XRD의 시라법에 의한 규소결정크기는 4.2 nm로 측정되었다.As shown in Table 1, the oxygen content analyzed by the elemental analyzer of the prepared carbon-silicon oxide composite was 36 wt% and the carbon content 5 wt%. The BET was 6.3 m 2 /g, the specific gravity was 2.2, the D 50 was 6 μm, and the silicon crystal size by XRD was measured to be 4.2 nm.
<비교예 2> 탄소-규소복합산화물 복합체의 제조<Comparative Example 2> Preparation of carbon-silicon composite oxide composite
상기 실시예 1에서 SiOx(x=1.2)를 사용하고 Mg 함량이 2 wt% 인 것을 제외하고, 실시예 1과 동일한 방법으로 탄소가 표면에 피복된 탄소-규소복합산화물 복합체 분말을 제조하였다.In Example 1, SiOx (x=1.2) was used and a carbon-silicon composite oxide composite powder coated with carbon was prepared in the same manner as in Example 1, except that the Mg content was 2 wt%.
상기 표 1에서 보는 바와 같이 상기 제조된 탄소-규소복합산화물 복합체의 마그네슘 함량은 2 wt% 이며, 원소분석기에 의하여 분석된 산소 함량은 39.6 wt%, 탄소 함량은 5 wt% 이였다. BET는 6.7 m 2/g 이며, 비중은 2.3, D 50은 6 μm, XRD의 시라법에 의한 규소결정크기는 9.1 nm로 측정되었다.As shown in Table 1, the magnesium content of the prepared carbon-silicon composite oxide composite was 2 wt%, the oxygen content analyzed by the elemental analyzer was 39.6 wt%, and the carbon content was 5 wt%. The BET was 6.7 m 2 /g, the specific gravity was 2.3, the D 50 was 6 μm, and the silicon crystal size by XRD was 9.1 nm.
<비교예 3> 탄소-규소복합산화물 복합체의 제조<Comparative Example 3> Preparation of carbon-silicon composite oxide composite
상기 실시예 1에서 SiOx(x=0.6)를 사용하고 Mg 함량이 23 wt% 인 것을 제외하고, 실시예 1과 동일한 방법으로 탄소가 표면에 피복된 탄소-규소복합산화물 복합체 분말을 제조하였다.In Example 1, a carbon-silicon composite oxide composite powder coated with carbon was prepared in the same manner as in Example 1, except that SiOx (x=0.6) was used and the Mg content was 23 wt%.
상기 표 1에서 보는 바와 같이 탄소-규소복합산화물 복합체의 마그네슘 함량은 23 wt% 이며, 원소분석기에 의하여 분석된 산소 함량은 19 wt%, 탄소 함량은 4 wt% 이였다. BET는 6.2 m 2/g 이며, 비중은 2.6, D 50은 7 μm, XRD의 시라법에 의한 규소결정크기는 28 nm로 측정되었다.As shown in Table 1, the magnesium content of the carbon-silicon composite oxide composite was 23 wt%, the oxygen content analyzed by the elemental analyzer was 19 wt%, and the carbon content was 4 wt%. The BET was 6.2 m 2 /g, the specific gravity was 2.6, the D 50 was 7 μm, and the silicon crystal size by XRD was measured to be 28 nm.
<제조예> 탄소-규소복합산화물 복합체를 포함하는 리튬이차전지의 제작<Preparation Example> Fabrication of a lithium secondary battery including a carbon-silicon composite oxide composite
상기 실시예 및 비교예에 따라 제조된 탄소-규소복합산화물 복합체 분말과 천연 흑연을 10:90의 중량비로 혼합하여 전극 활물질로서 리튬 이차 전지용 음극과 전지(코인셀)를 제작하였다.The carbon-silicon composite oxide composite powder prepared according to the above Examples and Comparative Examples and natural graphite were mixed in a weight ratio of 10:90 to prepare a negative electrode for a lithium secondary battery and a battery (coin cell) as an electrode active material.
상기 혼합된 활물질과 바인더인 카르복시메틸셀룰로오즈(CMC,carboxyl methyl cellulose)와 스티렌부타디엔러버(SBR, styrene butadiene rubber)를 중량비가 97:1.5:1.5가 되도록 정량한 후 물과 혼합하여 음극 슬러리 조성물을 제조하였다.The mixed active material and the binder, carboxyl methyl cellulose (CMC) and styrene butadiene rubber (SBR) were quantified so that the weight ratio was 97:1.5:1.5, and then mixed with water to prepare a negative electrode slurry composition. I did.
상기 음극 술러리 조성물을 두께 18 ㎛의 동박에 도포해서 건조시킴으로써 두께 70 ㎛의 전극을 제조하였고, 상기 전극을 직경 14 mm의 원형으로 펀칭해서 코인셀용 음극을 제조하였고, 반대극으로 두께 0.3 ㎜의 금속리튬박을 사용하였다.An electrode having a thickness of 70 µm was prepared by applying the negative electrode library composition to a copper foil having a thickness of 18 µm and drying it, and punching the electrode into a circle having a diameter of 14 mm to prepare a negative electrode for a coin cell, Metal lithium foil was used.
분리막으로 두께 0.1 ㎜의 다공질폴리에틸렌시트를 사용하였고, 전해액으로 에틸렌카보네이트(EC)와 디에틸렌카보네이트(DEC)를 체적비 1:1로 혼합한 용액에 1M 농도의 LiPF 6를 용해시켜 전해질로 사용하였으며, 상기의 구성요소들을 적용하여 두께 2 ㎜, 직경 32 ㎜(소위 2032형)의 코인셀(전지)을 제작하였다.A porous polyethylene sheet having a thickness of 0.1 mm was used as a separator, and LiPF 6 at a concentration of 1 M was dissolved in a solution in which ethylene carbonate (EC) and diethylene carbonate (DEC) were mixed at a volume ratio of 1:1 as an electrolyte, and used as an electrolyte. A coin cell (battery) having a thickness of 2 mm and a diameter of 32 mm (so-called 2032 type) was manufactured by applying the above components.
<실험예> 전기화학 특성 평가<Experimental Example> Evaluation of electrochemical properties
상기 제조예에서 시료마다 제작한 코인셀을 0.1 C의 정전류로 전압이 0.005 V가 될 때까지 충전하고, 0.1 C의 정전류로 전압이 2.0 V가 될 때까지 방전하여 충전 용량(mAh/g), 방전 용량(mAh/g) 및 초기 충/방전 효율(%)을 구하였다.In the above preparation example, the coin cell prepared for each sample was charged with a constant current of 0.1 C until the voltage became 0.005 V, and discharged with a constant current of 0.1 C until the voltage became 2.0 V, and the charging capacity (mAh/g), Discharge capacity (mAh/g) and initial charge/discharge efficiency (%) were calculated.
또한, 상기 제조예에서 시료마다 제작한 코인셀을 1회 충전과 방전을 시킨 후 2회부터의 충전과 방전에서는 0.5 C의 정전류로 전압이 0.005 V가 될 때까지 충전하고, 0.5 C의 정전류로 전압이 2.0 V가 될 때까지 방전하여 사이클 특성(용량유지율)을 구하였다.In addition, after charging and discharging the coin cell produced for each sample in the above preparation example once, in charging and discharging from the second time, charging with a constant current of 0.5 C until the voltage becomes 0.005 V, and with a constant current of 0.5 C. It was discharged until the voltage became 2.0 V, and the cycle characteristic (capacity retention rate) was calculated|required.
상기 충전과 방전 용량, 초기 충/방전 효율 및 용량 유지율 분석결과를 하기 표 2에 나타내었다.The charging and discharging capacity, initial charging/discharging efficiency, and capacity retention analysis results are shown in Table 2 below.
초기충전용량 (mAh/g)Initial charging capacity (mAh/g) 초기방전용량 (mAh/g)Initial discharge capacity (mAh/g) 초기충/방전효율(mAh/g)Initial charge/discharge efficiency (mAh/g) 50 사이클후 용량유지율 (%)Capacity retention rate after 50 cycles (%)
실시예 1Example 1 515515 437437 8585 8787
실시예 2Example 2 510510 454454 8989 9292
실시예 3Example 3 503503 463463 9292 8686
실시예 4Example 4 505505 434434 8686 9090
실시예 5Example 5 502502 450450 8686 8787
비교예 1Comparative Example 1 556556 366366 6666 8181
비교예 2Comparative Example 2 491491 410410 8383 7676
비교예 3Comparative Example 3 500500 412412 8282 6565
표 2에서 보는 바와 같이, 본 발명에 따라 0. 5 < (산소) / (규소) + (마그네슘) <1.05 범위 내로 제조된 결정질 Si와 MgSiO 3로 이루어진 탄소-규소복합산화물 복합체를 포함하는 실시예에서 제조된 음극활물질을 포함하는 전지에서 방전 용량 및, 초기 효율이 우수하게 나타났으며 용량율도 50 사이클 후에 높게 유지되었다. 이로부터 Si, SiO 2와 Mg를 반응시켜 Si-MgSiO 3-Mg 2SiO 4-SiOx-C계 음극활물질로 제조되어, 산화규소(SiOx)의 높은 방전 용량은 유지시키면서 비가역요소를 제거하여 초기 충/방전 효율을 향상시키는 것을 알 수 있었다.As shown in Table 2, an example including a carbon-silicon composite oxide composite consisting of crystalline Si and MgSiO 3 prepared in the range of 0.5 <(oxygen) / (silicon) + (magnesium) <1.05 according to the present invention Discharge capacity and initial efficiency were excellent in the battery containing the negative active material prepared in, and the capacity ratio was also maintained high after 50 cycles. From this, Si, SiO 2 and Mg are reacted to produce a Si-MgSiO 3- Mg 2 SiO 4- SiOx-C-based negative electrode active material, while maintaining the high discharge capacity of silicon oxide (SiOx) and removing irreversible elements for initial charging. /It was found that the discharge efficiency was improved.
비교예 1에서 마그네슘을 사용하지 않고 제조된 산화규소(SiOx)는 초기 충/방전 효율이 66%로 MgSiO 3 또는 Mg 2SiO 4가 포함된 실시예의 탄소-규소복합산화물 복합체에 비하여 낮게 나타났다.Silicon oxide (SiOx) prepared without using magnesium in Comparative Example 1 had an initial charge/discharge efficiency of 66%, which was lower than that of the carbon-silicon composite oxide composite of Example containing MgSiO 3 or Mg 2 SiO 4 .
비교예 2 및 비교예 3에서 0. 5 <(산소 원자비율) / (규소 원자비율) + (마그네슘 원자비율) < 1.05 범위를 벗어난, 규소-산화규소-탄소 복합체는 수명 특성이 나빠지는 것을 알 수 있었다.In Comparative Examples 2 and 3, it was found that the life characteristics of the silicon-silicon oxide-carbon composite outside the range of 0.5 <(oxygen atomic ratio) / (silicon atomic ratio) + (magnesium atomic ratio) <1.05 are deteriorated. Could
이상으로 본 발명 내용의 특정한 부분을 상세히 기술하였는 바, 당업계의 통상의 지식을 가진 자에게 있어서, 이러한 구체적 기술은 단지 바람직한 실시 양태일 뿐이며, 이에 의해 본 발명의 범위가 제한되는 것이 아닌 점은 명백할 것이다. 따라서 본 발명의 실질적인 범위는 첨부된 청구항들과 그것들의 등가물에 의하여 정의된다고 할 것이다.As described above, specific parts of the present invention have been described in detail, and for those of ordinary skill in the art, it is obvious that these specific techniques are only preferred embodiments, and the scope of the present invention is not limited thereby. something to do. Therefore, it will be said that the practical scope of the present invention is defined by the appended claims and their equivalents.

Claims (21)

  1. 규소계활물질, 산화규소계활물질(SiO X, 0<x≤2)및 규산마그네슘 결정을 포함하는 규소복합산화물이며, It is a silicon composite oxide containing a silicon-based active material, a silicon oxide-based active material (SiO X , 0<x≤2), and a magnesium silicate crystal,
    표면이 탄소로 피복되어 있으며, The surface is covered with carbon,
    상기 규소복합산화물을 구성하는 각각의 원소의 원자 비율이 아래 관계식을 만족하는 것인 이차전지 음극재용 탄소-규소복합산화물 복합체.A carbon-silicon composite oxide composite for a secondary battery negative electrode material in which the atomic ratio of each element constituting the silicon composite oxide satisfies the following relationship.
    0. 5 <(산소 원자비율) / (규소 원자비율) + (마그네슘 원자비율) <1.050.5 <(atomic ratio of oxygen) / (atomic ratio of silicon) + (atomic ratio of magnesium) <1.05
  2. 제 1 항에 있어서,The method of claim 1,
    상기 규소복합산화물을 구성하는 원소의 원자 비율이 아래 관계식을 만족하는 것인 이차전지 음극재용 탄소-규소복합산화물 복합체.A carbon-silicon composite oxide composite for a secondary battery negative electrode material in which an atomic ratio of an element constituting the silicon composite oxide satisfies the following relational expression.
    2.0 < (규소 원자비율) / (마그네슘 원자비율) < 25.0 2.0 <(silicon atomic ratio) / (magnesium atomic ratio) <25.0
  3. 제 1 항에 있어서, The method of claim 1,
    X선 회절 패턴 분석 시 회절각 28 ° < 2θ < 29 °범위 내에서 규소계 활물질의 규소 결정에 귀속되는 피크가 나타나고,When analyzing the X-ray diffraction pattern, a peak attributed to the silicon crystal of the silicon-based active material appears within the diffraction angle of 28 ° <2θ <29 °,
    결정자 크기가 3 내지 20 nm 인 것을 특징으로 하는 이차전지 음극재용 탄소-규소복합산화물 복합체.A carbon-silicon composite oxide composite for a secondary battery anode material, characterized in that the crystallite size is 3 to 20 nm.
  4. 제 1 항에 있어서, The method of claim 1,
    상기 규소복합산화물 전체 100 중량부 당 마그네슘를 1 내지 15 중량부의 비율로 포함하는 것인 Containing magnesium in a ratio of 1 to 15 parts by weight per 100 parts by weight of the total silicon composite oxide
    이차전지 음극재용 탄소-규소복합산화물 복합체.Carbon-silicon composite oxide composite for negative electrode materials of secondary batteries.
  5. 제 1 항에 있어서, The method of claim 1,
    X선 회절 패턴 분석 시 회절각 28 ° < 2θ < 29 °범위 내에서 규소 결정에 귀속되는 피크가 나타나고, When analyzing the X-ray diffraction pattern, a peak attributed to the silicon crystal appears within the diffraction angle of 28 ° <2θ <29 °,
    회절각 30.5 ° < 2θ < 31.5 °범위 내에서 MgSiO 3 결정에 귀속되는 피크가 나타나는 것을 특징으로 하는 Characterized in that a peak attributable to the MgSiO 3 crystal appears within the diffraction angle of 30.5 ° <2θ <31.5 °
    이차전지 음극재용 탄소-규소복합산화물 복합체.Carbon-silicon composite oxide composite for negative electrode materials of secondary batteries.
  6. 제 5 항에 있어서, The method of claim 5,
    Mg 2SiO 4 결정을 더 포함하는 것을 특징으로 하는 Mg 2 SiO 4 characterized in that it further comprises a crystal
    이차전지 음극재용 탄소-규소복합산화물 복합체.Carbon-silicon composite oxide composite for negative electrode materials of secondary batteries.
  7. 제 1 항에 있어서, The method of claim 1,
    상기 규소복합산화물 100 중량부 당 탄소는 2 내지 15 중량부의 비율로 피복되어 있는 것을 특징으로 하는 It characterized in that the carbon per 100 parts by weight of the silicon composite oxide is coated in a ratio of 2 to 15 parts by weight.
    이차전지 음극재용 탄소-규소복합산화물 복합체.Carbon-silicon composite oxide composite for negative electrode materials of secondary batteries.
  8. 제 7 항에 있어서, The method of claim 7,
    탄소 피막의 평균 두께는 5 내지 200 nm 인 것을 특징으로 하는 The average thickness of the carbon film is 5 to 200 nm, characterized in that
    이차전지 음극재용 탄소-규소복합산화물 복합체.Carbon-silicon composite oxide composite for negative electrode materials of secondary batteries.
  9. 제 8항에 있어서, The method of claim 8,
    상기 탄소 피막은 탄소 나노 섬유, 그래핀, 산화 그래핀 및 산화 그래핀이 환원된 그래핀으로 이루어진 그룹에서 선택되는 어느 하나 이상을 포함하는 것을 특징으로 하는 이차전지 음극재용 탄소-규소복합산화물 복합체.The carbon film comprises at least one selected from the group consisting of carbon nanofibers, graphene, graphene oxide, and graphene in which graphene oxide is reduced. Carbon-silicon composite oxide composite for a secondary battery negative electrode material.
  10. 제 1 항에 있어서, The method of claim 1,
    상기 탄소-규소복합산화물 복합체의 평균 입경은 2 내지 10 μm 인 것을 특징으로 하는 이차전지 음극재용 탄소-규소복합산화물 복합체.The carbon-silicon composite oxide composite for a secondary battery negative electrode material, characterized in that the average particle diameter of the carbon-silicon composite oxide composite is 2 to 10 μm.
  11. 제 1 항에 있어서, The method of claim 1,
    상기 탄소-규소복합산화물 복합체의 비표면적은 3 내지 20 m 2/g 인 것을 특징으로 하는 이차전지 음극 재용 탄소-규소복합산화물 복합체.The carbon-silicon composite oxide composite for secondary battery negative electrode material, characterized in that the specific surface area of the carbon-silicon composite oxide composite is 3 to 20 m 2 /g.
  12. 규소 분말과 이산화규소 분말을 혼합하여 Si / SiO 2 원료분말혼합체를 준비하는 제 1 단계와, A first step of preparing a Si / SiO 2 raw material powder mixture by mixing silicon powder and silicon dioxide powder, and
    상기 Si / SiO 2 원료분말혼합체와 금속 마그네슘을 증발 및 증착시켜 규소복합산화물을 형성하는 제 2 단계;A second step of forming a silicon composite oxide by evaporating and depositing the Si / SiO 2 raw material powder mixture and metal magnesium;
    제 2 단계에서 제조된 규소복합산화물을 냉각시키는 제 3 단계;A third step of cooling the silicon composite oxide prepared in the second step;
    제 3 단계에서 제조된 규소복합 산화물을 분쇄/분급하는 제 4 단계;A fourth step of grinding/classifying the silicon composite oxide prepared in the third step;
    제 4 단계에서 제조된 규소복합산화물의 표면을 탄소로 피복시키는 제 5 단계;를 포함하는 Including a fifth step of coating the surface of the silicon composite oxide prepared in the fourth step with carbon
    제 1 항에 의한 이차전지 음극재용 탄소-규소복합산화물 복합체의 제조방법.A method for producing a carbon-silicon composite oxide composite for a negative electrode material for a secondary battery according to claim 1.
  13. 제 12 항에 있어서,The method of claim 12,
    상기 제 1 단계에 사용 규소 분말 및 이산화규소 분말은 각각 평균 입경이 50 nm 내지 50 μm 및 10 내지 100 nm 인 것인The silicon powder and the silicon dioxide powder used in the first step have an average particle diameter of 50 nm to 50 μm and 10 to 100 nm, respectively.
    이차전지 음극재용 탄소-규소복합산화물 복합체의 제조방법.Method for producing a carbon-silicon composite oxide composite for a secondary battery negative electrode material.
  14. 제 12 항에 있어서,The method of claim 12,
    상기 제 1 단계에 Si / SiO 2 원료 분말 혼합체는 규소 1 몰 당 이산화규소를 0.2 내지 1.5 몰의 비율로 혼합하는 것인In the first step, the Si / SiO 2 raw material powder mixture is a mixture of 0.2 to 1.5 moles of silicon dioxide per mole of silicon.
    이차전지 음극재용 탄소-규소복합산화물 복합체의 제조방법.Method for producing a carbon-silicon composite oxide composite for a secondary battery negative electrode material.
  15. 제 12 항에 있어서,The method of claim 12,
    상기 제 1 단계에서 Si는 산소를 포함할 수 있고, Si/SiO 2 원료 분말 혼합체의 (산소 원자/규소 원자)의 비율이 1 내지 1.1 것인In the first step, Si may contain oxygen, and the ratio of (oxygen atom/silicon atom) of the Si/SiO 2 raw material powder mixture is 1 to 1.1.
    이차전지 음극재용 탄소-규소복합산화물 복합체의 제조방법.Method for producing a carbon-silicon composite oxide composite for a secondary battery negative electrode material.
  16. 제 12 항에 있어서,The method of claim 12,
    상기 제 2 단계의 증발은 0.0000001 내지 2torr의 압력 하에서 600 내지 1600 ℃로 가열하여 수행되는 것인The evaporation of the second step is performed by heating to 600 to 1600 °C under a pressure of 0.0000001 to 2 torr.
    이차전지 음극재용 탄소-규소복합산화물 복합체의 제조방법.Method for producing a carbon-silicon composite oxide composite for a secondary battery negative electrode material.
  17. 제 12 항에 있어서,The method of claim 12,
    상기 제 3 단계의 냉각 과정은 수냉 기판에 의한 냉각, 또는 자연 냉각에 의해 상온까지 냉각되는 것인The cooling process of the third step is cooled to room temperature by cooling by a water-cooled substrate or by natural cooling.
    이차전지 음극재용 탄소-규소복합산화물 복합체의 제조방법.Method for producing a carbon-silicon composite oxide composite for a secondary battery negative electrode material.
  18. 제 12 항에 있어서,The method of claim 12,
    상기 제 4 단계의 분쇄/분급 과정은 평균 입경이 2.0 내지 10 μm 인 입자가 되도록 분쇄/분급하는 것인The pulverization/classification process of the fourth step is pulverization/classification so that particles having an average particle diameter of 2.0 to 10 μm are obtained.
    이차전지 음극재용 탄소-규소복합산화물 복합체의 제조방법.Method for producing a carbon-silicon composite oxide composite for a secondary battery negative electrode material.
  19. 제 12 항에 있어서,The method of claim 12,
    상기 탄소-규소복합산화물 복합체의 표면을 탄소로 피복하는 제 5 단계에서는 하기 화학식 1, 화학식 2 와 화학식 3으로 표시되는 화합물 중에서 하나 이상을 포함하는 탄소원 가스와, 탄산 가스, 아르곤, 수증기, 헬륨, 질소, 수소 중에서 하나 이상을 포함하는 불활성 가스를 투입하여 600 내지 1200 ℃에서 가스 상태로 반응시키는 것인 이차전지 음극재용 탄소-규소복합산화물 복합체의 제조방법.In the fifth step of coating the surface of the carbon-silicon composite oxide composite with carbon, a carbon source gas containing at least one of the compounds represented by the following Formulas 1, 2 and 3, carbon dioxide gas, argon, water vapor, helium, A method of producing a carbon-silicon composite oxide composite for a secondary battery negative electrode material to react in a gaseous state at 600 to 1200° C. by introducing an inert gas containing at least one of nitrogen and hydrogen.
    [화학식 1] C nH (2n+2-A)[OH] A [Formula 1] C n H (2n+2-A) [OH] A
    상기 화학식 1 중, n은 1 내지 20의 정수, A는 0 또는 1이며,In Formula 1, n is an integer of 1 to 20, A is 0 or 1,
    [화학식 2] C nH (2n-A) [Formula 2] C n H (2n-A)
    상기 화학식 2 중, n은 2 내지 6의 정수이고, A는 0 또는 1이며In Formula 2, n is an integer of 2 to 6, A is 0 or 1,
    [화학식 3] C xH yO z [Chemical Formula 3] C x H y O z
    상기 화학식 3 중, x는 0 또는 1 내지 20의 정수이고, y는 0 또는 1 내지 20의 정수이고, z는 0, 1 또는 2이다. In Formula 3, x is 0 or an integer of 1 to 20, y is 0 or an integer of 1 to 20, and z is 0, 1 or 2.
  20. 제 1 항 내지 제 11 항 중 어느 한 항의 탄소-규소복합산화물 복합체를 포함하는 Any one of claims 1 to 11 comprising the carbon-silicon composite oxide composite
    리튬이차전지. Lithium secondary battery.
  21. 제 20 항에 있어서,The method of claim 20,
    흑연을 더 포함하는 것인 Which further comprises graphite
    리튬이차전지.Lithium secondary battery.
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